• Obviously you yourself want be satisfied with the completed work.
• Building Controlthe local authority department which deals with the Building Regulations (England, Wales, N.I.) and Building StandardsIn Scotland, the system administered by a local authority for granting permission for work to be done (Building Warrant) and for a completed building to be occupied (Completion Certificate) (Scotland) can issue a completion certificate. See below
• Your architect can issue a certificate of completion. See below
• Your lender (if you have one) needs to be satisfied about releasing final payments. They may require either of the two above or they may want to rely on a surveyor’s report (usually a surveyor who they nominate and you pay for)
• You can pay off your builder
• The NHBCThe National House-Building Council describes itself as being "the leading warranty and insurance provider and standards setter for UK house-building for new and newly converted homes" (Solo) insurance (if you opt for this cover) comes into effect on completion and lasts for ten years. Same if you choose the Build Zone warranty
• Building site insurance can cease on completion and normal building insurance take over
• VAT can probably be claimed on completion. See more
• An EPCenergy performance certificate is required
• note that the Home Information Pack requirement has been suspended.

Building Control and Building Standards can issue a completion certificate providing the various stages of inspection have gained approval. This certificate may be required by your lender, solicitor or if you sell the house on in future. It shows that the main stages of the building works have been completed so far as can be reasonably ascertained by a building inspector. The Benchmark certificationA certification scheme for installers in the building industry. This includes Electrical, Heating, and MCSMicrogeneration Certification Scheme. MCS is an eligibility requirement for the Government's financial incentives, which include the Feed-in Tariff and the Renewable Heat Incentive. See the MCS web site Certification for Solar Electric, Solar Heating and Heat Pump Installers. These installers can self certify their own work for Building Regulations approval. See the Benchmark web site system is also included in this.

The certificate does not guarantee that there are no hidden problems and it is not insurance cover. If you were to sell the house on some time after completion then usually this certificate is what the buyer would ask to see, probably along with an up to date surveyor’s report.

In Scotland, prior to the occupation of a new property a ‘habitation certificate’ needs to be issued by Building Standards. This would be in the form of either a Temporary Occupation/Use Certificate or Certificate of Completion. (It is an offence to occupy a building without one or the other).

Your architect (if you use one) can issue a ‘final completion certificate’ (possibly – though unlikely for a small job such as a house – after interim certificates). This may be all your lender needs, to release a final stage payment of the mortgage. This certificate basically states that the building has been completed according to the plans and is usually based on visits made by the architect during the building work. It does not imply that there are no hidden defects which might come to light later and it is not the same as insurance cover such as is provided by an NHBC certificate. If some problem did show up later then you could try to sue your architect and prove they acted negligently in not spotting the problem. However this is not the same as them getting the design wrong. An architect is supposed to get the design right. But an architect is not expected to be able to spot dodgy practices by unscrupulous or inept builders who are able to cover up their mistakes before they are spotted

MATERIAL CHANGE OF USE

This might become relevant during alteration, conversion and extension work, e.g. the conversion of a barn or outbuilding into a house.

Requirement Cl (2), which addresses resistance to contaminants, is now added to the requirements in Regulation 6 of the Building Regulations 2010 which should be complied with when there are certain material changes of use of buildings. Regulation 6 sets out which parts of Schedule 1 should be complied with when there is a material change of use of the building as defined in Regulation 5. The absence of such a requirement would have meant that occupiers of buildings in areas at risk from contaminants may remain unprotected after the building work to effect the change of use is complete.

In particular, some contaminants can penetrate the floors of buildings such as landfill gas arising from the deposition of waste and vapours from spills of organic solvents and fuel. These contaminants can also migrate laterally from land outside the building. In order to deal with this Requirement C1 (2) now applies to all changes of use that have a residential purpose or provide sleeping accommodation including hotels, i.e. as defined by Regulation 5 (a) to 5 (g) with the exception of 5 (e) public buildings and 5 (j) shops. Other types of buildings are covered by Health and Safety legislation so do not need addressing through the Building Regulations, for example workplace assessment, including radon measurements.

Attention is drawn to the following extracts from the Building Regulations 2010.

Interpretation (Regulation 2)

‘Room for residential purposes’ means a room, or suite of rooms, which is not a dwelling-house or a flat and which is used by one or more persons to live and sleep and includes a room in a hostel, a hotel, a boarding house, a hall of residence or a residential home, but does not include a a room in a hospital, or other similar establishment, used for patient accommodation.

Meaning of material change of use (Regulation 5)

For the purposes of paragraph 8 (1)(e) of Schedule 1 to the Act and for the purposes of these Regulations, there is a material change of use where there is a change in the purposes for which or the circumstances in which a building is used, so that after the change:

a. the building is used as a dwelling, where previously it was not;

b. the building contains a flat, where previously it did not;

c. the building is used as a hotel or boarding house, where previously it was not;

d. the building is used as an institution, where previously it was not;

e. the building is used as a public building, where previously it was not;

f. the building is not a building described in Classes 1 to 6 in Schedule 2, where previously it was;

g. the building, which contains at least one dwelling, contains a greater or lesser number of dwellings than it did previously;

h. the building contains a room for residential purposes, where previously it did not;

i. the building, which contains at least one room for residential purposes, contains a greater or lesser number of such rooms than it did previously; or

j. the building is used as a shop, where previously it was not.

Requirements relating to material change of use (Regulation 6)

At this stage it is worth bearing in mind that Habitat Protection may need considering

1. Where there is a material change of use of the whole of a building, such work, if any, shall be carried out as is necessary to ensure that the building complies with the applicable requirements of the following paragraphs of Schedule 1:

a. in all cases,

B1 (means of warning and escape)

B2 (internal fire spread — linings)

B3 (internal fire spread — structure)

B4 (2) (external fire spread — roofs)

B5 (access and facilities for the fire service)

C2 (2) (interstitial and surface condensation)

F1 (ventilation)

G1 (cold water supply)

G3 (1) to (3) (hot water supply and systems)

G4 (sanitary conveniences)

G5 (bathrooms)

G6 (kitchens and good preparation areas)

H1 (foul water drainage)

H6 (solid waste storage)

J1 to J4 (combustion appliances)

L1 (conservation of fuel and power — dwellings);

P1 (electrical safety);

b. in the case of a material change of use described in Regulations 5(c), (d), (e) or (f), A1 to A3 (structure);

c. in the case of a building exceeding fifteen metres in height, B4 (1) (external fire spread — walls);

d. in the case of a material change of use described in regulation 5(a), (b), (c), (d), (g), (h), (i) or, where the material charge provides new residential accommodation, (f), C1 (2) (resistance to contaminents);

e. in the case of material change of use described in regulation 5(a), C2 (resistance to moisture);

f. in the case of a material change of use described in regulation 5(a), (b), (c), (g), (h) or (i), E1 to E3 (resistance to the passage of sound);

g. in the case of a material change of use described in regulation 5(e), where the public building consists or contains a school, E4 (acoustic conditions in schools);

h. in the case of a material change of use described in Regulation 5(a) or (b), G2 (water efficiency) and G3(4) (hot water supply and systems: hot water supply to fixed baths);

i. in the case of a material change of use described in regulation 5(c), (d), (e) or (j), M1 (access and use).

2. Where there is a material change of use of part only of a building, such work, if any, shall be carried out as is necessary to ensure that:

a. that part complies in all cases with any applicable requirement referred to in paragraph (1) (a);

b. in a case to which sub-paragraphs (b), (e), (f), (g) or (h) of paragraph (1) apply, that part complies with the requirements referred to in the relevant sub-paragraph; and

c. in the case to which sub-paragraph (c) of paragraph (1) applies, the whole building complies with the requirement referred to in that sub-paragraph; and

d. in the case to which sub-paragraph (i) of paragraph (1) applies:

i. that part and any sanitary appliances provided in or in connection with that part comply with the requirements referred to in that sub-paragraph; and

ii. the building complies with requirement M1 (a) of Schedule 1 to the extent that reasonable provision is made to provide either suitable independent access to that part or suitable access through the building to that part.

Historic buildings

Material change of use or alterations to existing buildings may include work on historic buildings. Historic buildings include:

a. listed buildings;

b. buildings situated in conservation areas;

c. buildings which are of architectural and historical interest and which are referred to as a material consideration in a local authority’s development plan;

d. buildings of architectural and historical interest within national parks, areas of outstanding natural beauty and world heritage sites.

There is a considerable amount of information about dealing with historic buildings on the SPAB web site.

The need to conserve the special characteristics of such historic buildings needs to be recognised. In such work, the aim should be to improve resistance to contaminants and moisture where it is practically possible, always provided that the work does not prejudice the character of the historic building, or increase the risk of long-term deterioration to the building fabric or fittings. In arriving at an appropriate balance between historic building conservation and improving resistance to contaminants and moisture it would be appropriate to take into account the advice of the local planning authority’s conservation officer.

Particular issues relating to work in historic buildings that warrant sympathetic treatment and where advice from others could therefore be beneficial include the following:

a. avoiding excessively intrusive gas protective measures;

b. ensuring that moisture ingress to the roof structure is limited and the roof can breathe. Where it is not possible to provide dedicated ventilation to pitched roofs it is important to seal existing service penetrations in the ceiling[for the purposes of part B of the Approved Documents] - A part of a building which encloses and is exposed overhead in a room, protected shaft or circulation space. (The soffit of a rooflight is included as part of the surface of the ceiling, but not the frame. An upstand below a rooflight would be considered as a wall.) and to provide draught proofing to any loft hatches. Any new loft insulation should be kept sufficiently clear of the eaves so that any adventitious ventilation is not reduced.

In most cases the rate at which gas seeps into buildings, mainly through floors, can be reduced by edge located sumps or sub-floor vents. These are less intrusive than internal sumps or ducts that may involve taking up floors. If flagged floors are taken up the stones should be indexed and their layout recorded to facilitate relaying when work is completed.

Radon can be dispersed by ventilation strategies such as positive pressurisation. These systems can often be accommodated in an unobtrusive manner.

If internal mechanical ventilation is used to disperse ground gases, it may affect the functioning of combustion appliances and may lead to the spillage of products of combustion into the building. Guidance on this can be found in Good Building Guide 25 Buildings and radon.

Section 0: General

C1

0.1 In the First Secretary of State’s view the requirements of C1 will be met by making reasonable provisions to secure the health and safety of persons in and about the building, and by safeguarding them and buildings against adverse effects of:

a. unsuitable material including vegetable matter, topsoil and pre-existing foundations;

Groundwater and drainage can be heavily influenced by SUDSSustainable urban drainage systems. Various ways of holding back rain water and allowing it to percolate into the ground instead of taking it to a drain and sewer. This helps prevent flash flooding. See Surface rainwater and SUDS .

b. contaminants on or in the ground covered, or to be covered, by the building and any land associated with the building; and

c. groundwater.

C2

0.2 In the First Secretary of State’s view the requirements of C2 will be met if the floors, walls and roof are constructed to protect the building and secure the health and safety of persons in and about the building from harmful effects caused by:

a. moisture emanating from the ground or from groundwater;

b. precipitation and wind-driven spray;

c. interstitial and surface condensation; and

d. spillage of water from or associated with sanitary fittings and fixed appliances.

INTRODUCTION TO PROVISIONS

0.3 Sections 1, 2 and 3 of this document cover Requirement C1 and deal with site preparation and resistance to contaminants under the headings ‘Clearance or treatment of unsuitable material’, ‘Resistance to contaminants’ and ‘Subsoil drainage’. Building Regulations are made for the purposes of securing the health, safety, welfare and convenience of persons in and about buildings. This means that action may need to be taken to mitigate the effects of contaminants within the land associated with the building as well as protecting the building and persons in and about the building.

0.4 Hazards associated with the ground may include the effects of vegetable matter including tree roots. They may include health hazards associated with chemical and biological contaminants, and gas generation from biodegradation of organic matter. Hazards to the built environment can be physical, chemical or biological. Items such as underground storage tanks or foundations may create hazards to both health and the building. Physical hazards also include unstable fill or unsuitable hardcore containing sulphate.

0.5 In addition, the naturally occurring radioactive gas radon and gases produced by some soils and minerals can be a hazard.

0.6 Sections 4, 5 and 6 of this document cover Requirement C2 and deal with resistance to moisture under the headings ‘Floors’, ‘Walls’ and ‘Roofs’. Moisture can rise from the ground to damage floors and the base of walls on any site, although much more severe problems can arise in sites that are liable to flooding. Driving rain or wind- driven spray from the sea or other water bodies adjacent to the building can penetrate walls or roofs directly, or through cracks or joints between elements, and damage the structure or internal fittings or equipment. Surface condensation from the water vapour generated within the building can cause moulds to grow which pose a health hazard to occupants. Interstitial condensation may cause damage to the structure. Spills and leaks of water, in rooms where sanitary fittings or fixed appliances that use water are installed (e.g. bathrooms and kitchens), may cause damage to floor decking or other parts of the structure.

0.7 The diagrams in this Approved DocumentThese are a part of the Building Regulations which ensure, if you follow them, that your plans will be automatically approved. The full set of the documents is available here have been set out to show typical situations and relationships between adjacent elements of construction. Conventional notations and hatching have been used to identify different materials. However, the diagrams cannot show specific situations. It remains the responsibility of the designer and builder to ensure that the building work meets all relevant aspects of the Building Regulations.

Flood risk

See the Environment Agency’s map on areas at risk from sea and river flooding

0.8 There is a presumption in planning guidance that development should not take place in areas that are at risk of flooding, Flood resistance is not currently a requirement in Schedule 1 of the Building Regulations 2000. However, when local considerations necessitate building in flood prone areas the buildings can be constructed to mitigate some effects of flooding such as:

a. elevated groundwater levels or flow of subsoil water across the site — this can be alleviated by the provision of adequate sub-soil drainage (see Section 3);

b. sewer flooding due to backflow or surcharging of sewers or drains — this can be addressed through the use of non-return valves and anti-flooding devices (see Section 3, paragraph 3.6);

c. intrusion of groundwater through floors — this can be addressed through the use of water resistant construction (see Section 4, paragraphs 4.7 to 4.12);

d. entry of water into floor voids — provision to inspect and clear out sub-floor voids can be considered (see Section 4, paragraph 4.20).

Further information on flood resistant construction can be found in a number of publications.

Land affected by contaminants

0.9 The guidance given on resistance to contaminants in Section 2 is for the purposes of the Building Regulations and their associated requirements. Users of this document should be aware that there may be further provisions for dealing with contaminants contained in planning guidance or legislation made under the regime set out in Part IIA of the Environmental Protection Act 1990 which may be supplementary to the requirements of the Building Regulations. The Contaminated Land (England) Regulations 2000 make detailed provisions of a procedural nature to help give full effect to the Part IIA regime, and the statutory guidance provides a basis for enforcing authorities to apply the regime. Where contaminants are removed, treated or contained as part of the construction works, waste management law may apply. If waste is removed for off-site disposal, the ‘Duty of Care’ and/or special waste requirements11 will apply.

0.10 Redevelopment is often the most effective means of remediating land affected by contaminants. This process is subject to controls under the Town and Country Planning Acts, and local planning authorities follow the guidance in PPG 23. Although environmental protection, planning and Building Regulations have different purposes their aims are similar. Consequently the processes for assessing the effects of pollutants and contaminants are similar. An investigation or assessment to determine the characteristics of a site can be further developed for Building Regulations purposes when the form and construction of the buildings are known. If appropriate data are gathered at the early stages it should not be necessary to completely re-evaluate a site for Building Regulations purposes.

Authorities that should be notified about contamination

0.11 Other regulatory authorities may have an interest in land affected by contamination. It may be necessary at any stage of the site investigation, risk assessment or remediation process to notify any unexpected events or change in outcomes to these regulatory authorities. The most likely situations are:

• The Environmental Health department of the district council should be informed if contaminants are found on a site where the presence of contamination has not been formally recognised through the planning process, if it is found that contaminants from the site are affecting other land or if contaminants are reaching the site from neighbouring land. Additional discussions may also be required if the contamination identified differs from that which has been previously discussed and agreed with the local planning authority (LPA) or Environmental Health department.

• As redevelopment is the most favoured means of dealing with land affected by contaminants, all land quality issues should be set out in documents in support of planning approval sent to the local planning authority. As designs are refined it may be necessary to inform the LPA of any impacts the design changes may have on the risk assessment and remediation strategy.

• The Environment Agency has a number of relevant duties at sites where contamination may be an issue; in particular these include specific duties relating to waste management and the protection of water quality and resources. Sites may be of concern to the Environment Agency where there is a potential impact on controlled waters, if the site is designated as a Special Site under Part IIA of the Environmental Protection Act 1991, where an authorisation may be required or specific hazards are found. The local Environment Agency office should be contacted to identify if there are any relevant issues.

• Some remedial measures may themselves require prior authorisation from the Environment Agency including abstraction licensing for groundwater treatment and waste management licensing for a number of activities involving contaminated soils.

• Working on contaminated land can be hazardous. The risks should be assessed to meet the requirements of the Construction (Design and Management) Regulations 1994. Working procedures should be in accordance with the Construction (Health, Safety and Welfare) Regulations 1996. It may be necessary to give notice to the Health and Safety Executive prior to work starting.

Specific guidance on the assessment of land affected by contaminants is set out in Appendix A.

see also:

Preparing for floods: interim guidance for improving the flood resistance of domestic and small business properties, ODPM, 2002.

Definitions

0.12 The following meanings apply to terms throughout this Approved Document:

Building and land associated with the building. The building and all the land forming the site subject to building operations which includes land under the building and the land around it which may have an effect on the building or its users (see also paragraph 2.11).

Contaminant. Any substance which is or may become harmful to persons or buildings, including substances which are corrosive, explosive, flammable, radioactive or toxic.

Floor. Lower horizontal surface of any space in a building including finishes that are laid as part of the permanent construction.

Groundwater. Water in liquid form, either as a static water table or flowing through the ground.

Interstitial condensation. Deposition of liquid water from a vapour, occurring within or between the layers of the building envelope.

Moisture. Water in liquid, solid or gaseous form.

Precipitation. Moisture in any form falling from the atmosphere, usually as rain, sleet, snow or hail.

Roof. Any part of the external envelope of a building that is at an angle of less than 700 to the horizontal.

Spray. Water droplets driven by the wind from the surface of the sea or other bodies of water adjacent to buildings. Sea spray can be especially hazardous to materials because of its salt content.

Surface condensation. Deposition of liquid water from a vapour, occurring on visible surfaces within the building.

Vapour control layer. Material of construction, usually a membrane, that substantially reduces the water vapour transfer through any building in which it is incorporated.

Wall. Any opaque part of the external envelope of a building that is at an angle of 70° or more to the horizontal.

Section 1: Clearance or treatment of unsuitable material

SITE INVESTIGATION

At this stage, archeological remains may come to light and Habitat Protection may also become an issue. Both of these matters can have an important impact on how the building process proceeds

1.1 The preparation of the site will depend on the findings of the site investigation. The site investigation is relevant to Sections 1, 2 and 3 of this Approved Document and also to the requirements of Approved Document A with respect to foundations. The site investigation should consist of a number of well-defined stages:

a. Planning stage. Clear objectives should be set for the investigation, including the scope and requirements, which enable the investigation to be planned and carried out efficiently and provide the required information;

b. Desk study. A review of the historical, geological and environmental information about the site is essential;

c. Site reconnaissance or walkover survey. This stage of the investigation facilitates the identification of actual and potential physical hazards and the design of the main investigation;

d. Main investigation and reporting. This will usually include intrusive and non-intrusive sampling and testing to provide soil parameters for design and construction. The main investigation should be preceded by (b) and (c) above.

1.2 The extent and level of investigation need to be tailored to the type of development and the previous use of land. Typically the site investigation should include susceptibility to groundwater levels and flow, underlying geology, and ground and hydro-geological properties. A geotechnical site investigation should identify physical hazards for site development, determine an appropriate design and provide soil parameters for design and construction. British Standard BSBritish Standard 5930:1999 provides comprehensive guidance on site investigations. Guidance on site investigation for low-rise buildings is given in six BREBuilding Research Establishment. Digests covering procurement, desk studies, the walk-over survey, trial pits, soil description and direct investigation. Reference should also be made to BS 8103-1 :1995.

1.3 Where the site is potentially affected by contaminants, a combined geotechnical and geo-environmental investigation should be considered. Guidance on assessing and remediating sites affected by contaminants is given in Section 2: Resistance to contaminants.

UNSUITABLE MATERIAL

1.4 Vegetable matter such as turf and roots should be removed from the ground to be covered by the building at least to a depth to prevent later growth. The effects of roots close to the building also need to be assessed. Consideration should be given to whether this provision need apply to a building used wholly for:

a. storing goods, provided that any persons who are habitually employed in the building are engaged only in taking in, caring for or taking out the goods; or

b. a purpose such that the provision would not serve to increase protection to the health or safety of any persons habitually employed in the building.

Alien vegetation such as Japanese Knotweed needs to spotted

1.5 Where mature trees are present on sites with shrinkable clays (see Diagram 1 and Table 1), the potential damage arising from ground heave to services and floor slabs and oversite concrete should be assessed. Reference should be made to BRE Digest 298. Where soils and vegetation type would require significant quantities of soil to be removed, reference should be made to BRE Digests 240 and 241, and to the FBE (Foundation for the Built Environment) report. The effects of remaining trees on services and building movements close to the building need to be assessed using guidance in NHBCThe National House-Building Council describes itself as being "the leading warranty and insurance provider and standards setter for UK house-building for new and newly converted homes" (National House Building Council) Standards Chapter 4.2.

1.6 Building services such as below ground drainage should be sufficiently robust or flexible to accommodate the presence of any tree roots. Joints should be made so that roots will not penetrate them. Where roots could pose a hazard to building services, consideration should be given to their removal.

1.7 On sites previously used for buildings, consideration should be given to the presence of existing foundations, services, buried tanks and any other infrastructure that could endanger persons in and about the building and any land associated with the building.

1.8 Where the site contains fill or made ground, consideration should be given to its compressibility and its potential for collapse on wetting, and to appropriate remedial measures to prevent damaging differential settlement. Guidance is given in BRE Digest 427 27 and BRE Report BR 424.

Section 2: Resistance to contaminants

INTRODUCTION

2.1 A wide range of solid, liquid and gaseous contaminants can arise on sites, especially those that have had a previous industrial use (see paragraph 0.12 for the definition of a contaminant). In particular, the burial of biodegradable waste in landfills can give rise to landfill gas (see paragraph 2.25). Sites with a generally rural use such as agriculture or forestry may be contaminated by pesticides, fertiliser, fuel and oils and decaying matter of biological origin.

2.2 Table 2 lists examples of sites that are likely to contain contaminants. It is derived from the ‘Industry Profile’ guides produced by the former Department of the Environment (DoE), each of which deals with a different industry with the potential to cause contamination. Each profile identifies contaminants which may be associated with the industry, areas on the site in which they may be found and possible routes for migration. The Department for the Environment, Food and Rural Affairs (Defra)/Environment Agency publication CLR 8 presents a selection of contaminants that may be relevant for the assessment of land affected by contaminants as they are likely to be found on a large number of industrial sites across the UK.

2.3 In addition, there can be problems of natural contaminants in certain parts of the country as a result of the underlying geology. In this instance the contaminants can be naturally occurring heavy metals (e.g. cadmium and arsenic) originating in mining areas, and gases (e.g. methane and carbon dioxide) originating in coal mining areas and from organic rich soils and sediments such as peat and river silts. The Environment Agency has produced two guidance documents on this subject which discuss the geographical extent of these contaminants, the associated hazards, methods of site investigation and protective measures.

2.4 Natural contaminants also include the radioactive gas radon, although the specific approach for assessing and managing the risks it poses is different from other contaminants (see paragraphs 2.39 to 2.41).

2.5 Sulphate attack affecting concrete floor slabs and oversite concrete associated with particular strata also needs to be considered. Principal areas of sulphate bearing strata in England and Wales are shown in Diagram 1 and Table 1. BRE Special Digest SD1 provides guidance on investigation, concrete specification and design to mitigate the effects of sulphate attack.

Note: the above list is not exhaustive

SOLID AND LIQUID CONTAMINANTS

Risk assessment

General concepts

2.6    To ensure safe development of land affected by contaminants the principles of risk assessment (as set out in paragraph 2.8 below) should be followed. The general approach is founded on the concept of the ‘source—pathway— receptor’ relationship, or pollutant linkage, where source refers to contaminants in or on the ground. This is illustrated by the conceptual model in Diagram 2.

2.7    When land affected by contaminants is developed, receptors (i.e. buildings, building materials and building services, as well as people) are introduced onto the site and so it is necessary to break the pollutant linkages. This can be achieved by:

a. treating the contaminant (e.g. use of physical, chemical or biological processes to eliminate or reduce the contaminant’s toxicity or harmful properties);

b. blocking or removing the pathway (e.g. isolating the contaminant beneath protective layers or installing barriers to prevent migration);

c. protecting or removing the receptor (e.g. changing the form or layout of the development, using appropriately designed building materials, etc.);

d. removing the contaminant (e.g. excavating contaminated material).

Stages of risk assessment

2.8    In assessing the risks for land contamination a tiered approach is adopted with an increasing level of detail required in progressing through the tiers. The three tiers are: preliminary risk assessment, generic quantitative risk assessment (GQRA) and detailed quantitative risk assessment (DQRA). Once the need for a risk assessment has been identified, it will always be necessary to undertake a preliminary risk assessment but, depending on the situation and the outcome, it may not be appropriate to do a more detailed risk assessment. Alternatively, it may be necessary to do only one or both of the more detailed risk assessments. For each tier, the model procedures for the management of land contamination (CLR 11, Consultation draft 2003) describes the stages of risk assessment that should be followed for identifying risks and making judgements about the consequences of land affected by contamination when developing a site. These are outlined below:

a. Hazard identification- developing the conceptual model by establishing contaminant sources, pathways and receptors. This is the preliminary site assessment which consists of a desk study and a site walk-over in order to obtain sufficient information to obtain an initial understanding of the potential risks. An initial conceptual model for the site can be based on this information.

b. Hazard assessment — identifying what pollutant linkages may be present and analysing the potential for unacceptable risks. Collect further information and undertake exploratory site investigation to refine understanding of risks and the likelihood of pollutant linkages. The results may be interpreted using generic criteria and assumptions.

c. Risk estimation — establishing the scale of the possible consequences by considering the degree of harm that may result and to which receptors. Undertake detailed ground investigation to collect sufficient data to estimate the risks the contaminants may pose to defined receptors under defined conditions of exposure.

d. Risk evaluation — deciding whether the risks are acceptable or unacceptable. Review all site data to decide whether estimated risks are unacceptable, taking into account the nature and scale of any uncertainties associated with the risk estimation process.

2.9    Guidance on the investigation of sites potentially affected by contaminants is provided in:

a. the Association of Geotechnical and Geoenvironmental Specialists (AGS) Document ;

b. BS 5930:1 999;

c. BS 101 75:2001; and

d. the Environment Agency documents 385.

They recommend a risk based approach to identify and quantify the hazards that may be present and the nature of the risk they may pose. They describe the design and execution of field investigations, including suitable sample distribution strategies, sampling and testing.

Hazard identification and assessment

2.10    A preliminary site assessment is required to provide information on the past and present uses of the site and surrounding area that may give rise to contamination (see Table 2). During the site walk-over there may be signs of possible contaminants (see Table 3). The information collated from the desk study and site walk-over can assist and will dictate the design of the exploratory and detailed ground investigation.

2.11     The site assessment and risk evaluation should pay particular attention to the area of the site subject to building operations. Those parts of the land associated with the building that include the building itself, gardens and other places on the site that are accessible to users of the building and those in and about the building should be remediated to the requirements of the Building Regulations.

There may be a case for a lower level of remediation if part of, or the remainder of, the land associated with the building, or adjacent to such land, is accessible to a lesser extent to the user or those in and about the building than the main parts of the buildings and their respective gardens. This incremental approach may also apply when very large sites are subject to redevelopment in stages; it may be possible to limit remediation to the site that is subject to building operations.

In all cases the risk evaluation and remediation strategy documentation is likely to be appropriate for demonstrating that restricted remediation is acceptable. The onus is on the applicant to show why part of a site may be excluded from particular remediation measures.

Even if the adjacent land is not subject to Building Regulations, which are concerned with health and safety, it may still be subject to planning control legislation or to control under Part IIA of the Environmental Protection Act 1990.

2.12     The Planning Authority should be informed prior to any intrusive investigations or if any substance is found which is at variance with any preliminary statements made about the nature of the site.

Risk estimation and evaluation

2.13     The detailed ground investigation must provide sufficient information for the confirmation of a conceptual model for the site, the risk assessment and the design and specification of any remedial works. This is likely to involve collection and analysis of soil, soil gas, surface and groundwater samples by the use of invasive and/or non-invasive techniques. An investigation of the groundwater regime, levels and flows is essential for most sites since elevated groundwater levels could bring contaminants close to the surface both beneath the building and in any land associated with the building. Expert advice should be sought but further guidance and information are provided in Annex A.

2.14 During the development of land affected by contaminants the health and safety of both the public and workers should be considered.

Remedial measures

Introduction

2.15    If unacceptable risks to the defined receptor have been identified then these need to be managed through appropriate remedial measures. The risk management objectives are defined by the need to break the pollutant linkages using the methods outlined in paragraph 2.6 and described below. Other objectives will also need to be considered such as timescale, cost, remedial works, planning constraints and sustainability. Depending on the contaminant, three generic types of remedial measures can be considered: treatment, containment and removal. The containment or treatment of waste may require a waste management licence from the Environment Agency.

When building work is undertaken on sites affected by contaminants where control measures are already in place, care must be taken not to compromise these measures. For example, cover systems may be breached when new building foundations are constructed, such as when extensions are added.

Treatment

2.16    A wide range of treatment processes is now available for dealing with contaminants. Biological, chemical and physical techniques carried out either in or ex situ exist which may decrease one or more of the following features of the contaminants: mass, concentration, mobility, flux or toxicity. The choice of the most appropriate technique for a particular site is a highly site-specific decision for which specialist advice should be sought.

Containment can mean leaving something alone which is already contained. An interesting example of this is the self build housing at Ashley Vale in Bristol where the houses were built on top of a vast, pre-existing concrete slab which covered polluted land.

Containment

2.17    Containment in its widest sense usually means encapsulation of material containing contaminants but in the context of building development containment is often taken to mean cover systems. However, in-ground vertical barriers may also be required to control lateral migration of contaminants.

2.18    Cover systems involve the placement of one or more layers of materials over the site to achieve one or more of the following objectives:

a. break the pollutant linkage between receptors and contaminants;

b. sustain vegetation;

c. improve geotechnical properties; and

d. reduce exposure to an acceptable level.

2.19    Some of the building structures, e.g. foundations, sub-structure and ground floor, may, dependent on the circumstances and construction, contribute to measures to provide effective protection of health from contaminants.

2.20     Imported fill and soil for cover systems should be assessed at source to ensure that it is not contaminated above specified concentrations and meets required standards for vegetation. Design and dimensioning of cover systems, particularly soil based ones typically used for gardens, should take account of their long-term performance where intermixing of the soil cover with the contaminants in the ground can take place. Maintenance and monitoring may be necessary. Gradual intermixing due to natural effects and activities such as burrowing animals, gardening, etc. needs to be considered.

Excavations by householders for garden features, etc. can penetrate the cover layer and may lead to exposure to contaminants. Further guidance on the design, construction and performance of cover layers is given in the Construction Industry Research and Information Association (CIRIAConstruction industry research and information association) Report SP124.

Removal

See also Ground Works

2.21     This involves the excavation and safe disposal to licensed landfill of the contaminants and contaminated material. Excavation can be targeted to contaminant ‘hot spots’, or it may be necessary to remove sufficient depth of contaminated material to accommodate a cover system within the planned site levels. Removal may not be viable depending on the extent and depth of the contaminants on the site and the availability of suitably licensed landfills. Imported fill should be assessed at source to ensure that there are no materials that will pose unacceptable risks to potential receptors.

2.22     Further detailed guidance on all three types of remedial measure is given in the Environment Agency/NHBC R & D Publication 66 referred to above and in a series of CIRIA publications.

Risks to buildings, building materials and services

2.23    The hazards to buildings, building materials and services on sites affected by contaminants need to be considered since these are also receptors. The hazards to consider are:

a. Aggressive substances. These include inorganic and organic acids, alkalis, organic solvents and inorganic chemicals such as sulphates and chlorides which may affect the long-term durability of construction materials (such as concrete, metals and plastics).

b. Combustible fill. This includes domestic waste, colliery spoil, coal, plastics, petrol- soaked ground, etc. which, if ignited, may lead to subterranean fires and consequent damage to the structural stability of buildings, and the integrity or performance of services.

c. Expansive slags. The two main types are blast furnace and steel making slag which may expand some time after deposition – usually when water is introduced onto the site -causing damage to buildings and services.

d. Floodwater affected by contaminants. Substances in the ground, waste matter or sewage may contaminate floodwater. This contaminated water may affect building elements, such as walls or ground floors, that are close to or in the ground. Guidance on resistant construction can be found in Preparing for floods or Design guidance on flood damage to dwellings.

2.24     Although the building and building materials are the main receptors with these hazards, ultimately there could be harm to health. A particular concern is the effect of hydrocarbons permeating potable water pipes made of polyethylene. Guidance on reducing these risks is given in a Water Research Centre report. Further guidance on the assessment and management of risks to building materials is given in an Environment Agency document.

METHANE AND OTHER GASES FROM THE GROUND

Introduction

2.25    The term ‘methane and other gases’ is used to define hazardous soil gases which either originate from waste deposited in landfill sites or are generated naturally. It does not include radon which is dealt with separately in paragraphs 2.39 to 2.41. However, the term does include volatile organic compounds (VOCsVolatile organic compounds). As stated in Limitations on Requirements above, measures described in this document are the minimum that are needed to comply with the Building Regulations. Further actions may be necessary to deal with the requirements of other legislation.

2.26    Landfill gas is generated by the action of micro-organisms on biodegradable waste materials in landfill sites. It generally consists of methane and carbon dioxide together with small quantities of VOCs which give the gas its characteristic odour. Methane and oxygen deficient atmospheres (sometimes referred to as stythe or black-damp) containing elevated levels of carbon dioxide and nitrogen can be generated naturally in coal mining areas. Methane and carbon dioxide can also be produced by organic rich soils and sediments such as peat and river silts. A wide range of VOCs can also be present as a result of petrol, oil and solvent spillages. Methane and other gases can migrate through the subsoil and through cracks and fissures into buildings.

2.27    Methane is an explosive and asphyxiating gas. Carbon dioxide although non-flammable is toxic. VOCs are not only flammable and toxic but can also have a strong, unpleasant odour. Should any of these gases build up to hazardous levels in buildings then they can cause harm to health or compromise safety.

Risk assessment

2.28     The risk assessment process outlined in paragraph 2.8 should also be adopted for methane and other gases. Further investigation for hazardous soil gases may be required where the ground to be covered by the building and/or any land associated with the building is:

a. On a landfill site, within 250m of the boundary[for the purposes of part B of the Approved Documents] - The boundary of the land belonging to the building, or where the land abuts a road, railway, canal or river, the centre line of that road, railway, canal or river (See Diagram 17.) of a landfill site or where there is suspicion that it is within the sphere of influence of such a site. The Environment Agency’s policy on building development on or near to landfills should be followed.

b. On a site subject to the wide scale deposition of biodegradable substances (including made ground or fill).

c. On a site that has been subject to a use that could give rise to petrol, oil or solvent spillages.

d. In an area subject to naturally occurring methane, carbon dioxide and other hazardous gases (e.g. hydrogen sulphide).

2.29    There are documents that cover hazardous soil gases in these specific contexts:

a. Waste Management Paper No. 27 gives guidance on the generation and movement of landfill gas as well as techniques for its investigation. Complementary guidance is given in a document by the Chartered Institution of Wastes Management (CIWM).

b. The Institute of Petroleum has prepared a guidance document covering petroleum retail sites.

c. The BGS report on naturally occurring methane and other gases gives guidance on the geographical extent of these contaminants, the associated hazards and methods of site investigation. This is supported by a report sponsored by the former DoE on methane and other gases in disused coal mining areas.

d. In addition, CIRIA has produced three relevant guidance documents on methane and other gases which describe how such gases are generated and move within the ground, methods of detection and monitoring and investigation strategies.

2.30    During a site investigation for methane and other gases it is important to take measurements over a sufficiently long period of time in order to characterise gas emissions fully. This should also include periods when gas emissions are likely to be higher, e.g. during periods of falling atmospheric pressure. It is also important to establish not only the concentration of these gases in the ground but also the quantity of gas generating materials, their rate of gas generation, gas movement in the ground and gas emissions from the ground surface. This is an important part of the risk estimation stage. Indications about the gas regime in the ground can be obtained through surface emission rate and borehole flow rate measurements, and guidance on this is given in CIRIA Reports 151 and 152.

2.31    Construction activities undertaken as part of building development can alter the gas regime on the site. For example, a site strip can increase surface gas emissions as can piling and excavation for foundations, and dynamic compaction can push dry biodegradable waste into moist, gas- active zones.

2.32    There are no Soil Guideline Values (see Annex A) for methane and other gases. When assessing gas risks in the context of traditional housing there is a need to consider two pathways for human receptors: (i) gas entering the dwelling through the sub-structure, and building up to hazardous levels, and (ii) subsequent householder exposure in garden areas which can include where outbuildings (e.g. garden sheds and greenhouses) and extensions are constructed, and where there may also be excavations for garden features (e.g. ponds).

2.33    Guidance on undertaking gas risk assessment is given in CIRIA Report 152, and the GaSIM model is also available for assessing gas emissions from landfill sites. There is further discussion of gas risk assessment in the forthcoming Defra/Environment Agency document CLR 11.

2.34    CIRIA Report 149 and the Department of the Environment, Transport and the Regions (DETR) Partners in Technology (PIT) report describe a range of ground gas regimes (defined in terms of soil gas concentrations of methane and carbon dioxide as well as borehole flow rate measurements) which can be helpful in assessing gas risks.

2.35    Depending on the proposed use, for non- domestic development the focus might be on the building only, but the general approach is the same.

Remedial measures

2.36    If the risks posed by the gas are unacceptable then these need to be managed through appropriate building remedial measures. Site-wide gas control measures may be required if the risks on any land associated with the building are deemed unacceptable. Such control measures include removal of the gas generating material or covering together with gas extraction systems. Further guidance is contained in CIRIA Report 149. Generally speaking, expert advice should be sought in these circumstances.

2.37    Gas control measures for dwellings consist of a gas resistant barrier across the whole footprint (i.e. walls and floor) above an extraction (or ventilation) layer from which gases can be dispersed and vented to the atmosphere. They are normally passive, i.e. gas flow is driven by stack (temperature difference) and wind effects. Consideration should be given to the design and layout of buildings to maximise the driving forces of natural ventilation. Further guidance on this and detailed practical guidance on the construction of protective measures for housing is given in the BRE/Environment Agency report BR 414 (In order to accommodate gas resistant membrane, for example as shown in BR414, the position and type of insulation may have to be adjusted). The DETR/Arup Environmental report compares the performance of a range of commonly used gas control measures and can be used as a guide to the design of such measures.

2.38    Gas control measures for non-domestic buildings use the same principles as those used for housing, and the DETR/Arup Environmental report can also be used as a guide to design. Expert advice should be sought as the floor area of such buildings can be large and it is important to ensure that gas is adequately dispersed from beneath the floor. The use of mechanical (as opposed to passive) systems and monitoring and alarm systems may be necessary. There is a need for continued maintenance and calibration of these systems, so they are more appropriate with non-domestic buildings (as opposed to dwellings) since there is usually scope for this. Again, expert advice should be sought. Special sub-floor ventilation systems are carefully designed to ensure adequate performance and should not be modified unless subjected to a specialist review of the design. Such ventilation systems, particularly those using powered ventilation, are unlikely to be appropriate for owner occupied properties as there is a risk of interference by users.

RADON

2.39    Radon is a naturally occurring radioactive colourless and odourless gas which is formed in small quantities by radioactive decay wherever uranium and radium are found. It can move through the subsoil and so into buildings. Some parts of the country, notably the West Country, have higher levels than elsewhere. Exposure to high levels for long periods increases the risk of developing lung cancer. To reduce this risk all new buildings, extensions and conversions, whether residential or non-domestic, built in areas where there may be elevated radon emissions, may need to incorporate precautions against radon.

2.40    Guidance on the areas susceptible to radon and practical protective measures has been published by the BRE as Report BR 211. This guidance was developed to show radon protective measures for dwellings.

A European Council Directive establishes a common basis for radiation protection legislation in all Member States. The Ionising Radiations Regulations set a national reference level for radon gas and employers and self-employed persons responsible for a workplace are required to measure radon levels on being directed to do so. See also the HSEHealth and Safety Executive. see also Health and Safety/BRE guide ‘Radon in the workplace’.

There is at present no guidance on protection from radon in the workplace but some of the techniques used for installing a radon resistant membrane, described in BR 211, may be suitable for use in domestic sized buildings with heating and ventilation regimes similar to those used in dwellings. The guidance in BR 211 can be used as the basis for radon protection of other building types but this should be done with caution. Information in ‘Radon in the workplace’ provides guidance for existing non-domestic buildings.

Interim guidance on extensions can be found in GBG 25 Buildings and radon.

2.41    Although the precise areas where measures should be taken are listed in the BRE Report, these are reviewed by DCLG in the light of advice from the National Radiological Protection Board (NRPB) and the British Geological Survey (BGS). Current information on the areas delineated by ODPM for the purposes of Building Regulations should be obtained from local authority building controlthe local authority department which deals with the Building Regulations officers or from approved inspectors. Changes to areas delineated as requiring radon protection will be notified to building control bodies and will be posted on the DCLG website.

Section 3: Subsoil drainage

see more on drains

3.1    The provisions which follow assume that the site of the building is not subject to general flooding (see paragraph 0.8) or, if it is, that appropriate steps are being taken.

3.2    Where the water table can rise to within 0.25m of the lowest floor of the building, or where surface water could enter or adversely affect the building, either the ground to be covered by the building should be drained by gravity, or other effective means of safeguarding the building should be taken.

3.3    If an active subsoil drain is cut during excavation and if it passes under the building it should be:

a. re-laid in pipes with sealed joints and have access points outside the building; or

b. re-routed around the building; or

c. re-run to another outfall (see Diagram 3).

3.4    Where there is a risk that groundwater beneath or around the building could adversely affect the stability and properties of the ground, consideration should be given to site drainage or other protection (see Section 4: Floors).

3.5    For protecting low lying buildings or basements from localised flooding where foul water drainage also receives rainwater, refer to Approved Document H (Drainage and waste disposal). In heavy rainfall these systems surcharge and where preventative measures are not taken this could lead to increased risks of flooding within the property.

3.6    Flooding can create blockages in drains and sewers that can lead to backflow of sewage into properties through low level drain gullies, toilets, etc. Guidance on anti-flooding devices is given in a CIRIA publication.

3.7    General excavation work for foundations and services can alter groundwater flows through the site. Where contaminants are present in the ground, consideration should be given to subsoil drainage to prevent the transportation of water-borne contaminants to the foundations or into the building or its services.

Section 4: Floors

see more on floors

4.1    This section gives guidance for five situations:

a. ground supported floors exposed to moisture from the ground (see paragraphs 4.6 to 4.12);

b. suspended timber ground floors exposed to moisture from the ground (see paragraphs 4.13 to 4.16);

c. suspended concrete ground floors exposed to moisture from the ground (see paragraphs 4.17 to 4.20);

d. the risk of interstitial condensation in ground floors and floors exposed from below (see paragraph 4.21);

e. the risk of surface condensation and mould growth on any type of floor (see paragraph 4.22).

4.2     Floors next to the ground should:

a. resist the passage of ground moisture to the upper surface of the floor;

b. not be damaged by moisture from the ground;

c. not be damaged by groundwater;

d. resist the passage of ground gases. To meet requirement C1 (2) floors in some localities may need to resist the passage of hazardous ground gases such as radon or methane. Remedial measures will include a gas resistant barrier which, with proper detailing, can also function as a damp proof membrane. For specific guidance for methane and other gases refer to paragraphs 2.25 to 2.38, and for radon refer to paragraphs 2.39 to 2.41. Guidance is provided in reports BR 414 and BR 211 respectively.

4.3    Consideration should be given to whether 4.2(a) need apply to a building used wholly for:

a. storing goods, provided that any persons who are habitually employed in the building are engaged only in taking in, caring for or taking out the goods; or

b. a purpose such that the provision would not serve to increase protection to the health or safety of any persons habitually employed in the building.

4.4   Floors next to the ground and floors exposed from below should be designed and constructed so that their structural and thermal performance are not adversely affected by interstitial condensation.

4.5    All floors should not promote surface condensation or mould growth, given reasonable occupancy conditions.

GROUND SUPPORTED FLOORS (MOISTURE FROM THE GROUND)

4.6    Any ground supported floor will meet the requirement if the ground is covered with dense concrete laid on a hardcore bed and a damp- proof membrane is provided. Suitable insulation may be incorporated.

Technical solution

4.7    Unless it is subjected to water pressure, which is likely in the case of buildings on very permeable strata such as chalk, limestone or gravel (in which case see Alternative approach, paragraph 4.12), a concrete ground supported floor may be built as follows (Diagram 4):

a. well compacted hardcore bed, no greater than 600mm deep, of clean, broken brick or similar inert material, free from materials including water-soluble sulphates in quantities which could damage the concrete (BRE Digest 276; and

b. concrete at least 100mm thick (but thicker if the structural design requires) to mix ST2 in BS 8500 or, if there is embedded reinforcement, to mix ST4 in BS 8500M; and

c. damp-proof membrane above or below the concrete, and continuous with the damp proof courses in walls, piers and the like. If the ground could contain water soluble sulphates, or there is any risk that sulphate or other deleterious matter could contaminate the hardcore, the membrane should be placed at the base of the concrete slab.

note the two units for measuring the thickness of polythene. (microns and gauge). Microns is the current way with gauge being a leftover from the old imperial standards still used in the USA.

4.8    A membrane below the concrete could be formed with a sheet of polyethylene, which should be at least 300μm thick (1200 gauge) with sealed joints and laid on a bed of material that will not damage the sheet.

4.9    A membrane laid above the concrete may be either polyethylene sheet as described above (but without the bedding material) or three coats of cold applied bitumen solution or similar moisture and water vapour resisting material. In each case it should be protected by either a screed or a floor finish, unless the membrane is pitchmastic or similar material which will also serve as a floor finish.

4.10    Insulants placed beneath floor slabs should have sufficient strength to resist the weight of the slab and the anticipated floor loading as well as any possible overloading during construction. In order to resist degradation insulation that is placed below the damp proof membrane should have low water absorption. If necessary the insulant should be resistant to contaminants in the ground.

4.11    A timber floor finish laid directly on concrete may be bedded in a material which may also serve as a damp-proof membrane. Timber fillets laid in the concrete as a fixing for a floor finish should be treated with an effective preservative unless they are above the damp- proof membrane. Some preservative treatments are described in BS 1282:1999.

Alternative approach

4.12    The requirement can also be achieved by following the relevant recommendations of Clause 11 of BS CP 102:1973. BS 81 02:1990 includes recommendations for floors subject to water pressure.

SUSPENDED TIMBER GROUND FLOORS (MOISTURE FROM THE GROUND)

see Floors and ceilings

4.13    Any suspended timber floor next to the ground will meet the requirement if:

a. the ground is covered so as to resist moisture and prevent plant growth; and

b. there is a ventilated air space between the ground covering and the timber; and

c. there are damp-proof courses between the timber and any material which can carry moisture from the ground.

Technical solution

4.14    Unless it is covered with a floor finish which is highly vapour resistant (in which case see the Alternative approach in paragraph 4.16), a suspended timber floor next to the ground may be built as follows (Diagram 5):

a. Ground covering either:

i. unreinforced concrete at least 100mm thick to mix ST 1 in BS 8500. The concrete should be laid on a compacted hardcore bed of clean, broken brick or any other inert material free from materials including water-soluble sulphates in quantities which could damage the concrete; or

ii. concrete, composed as described above, or inert fine aggregategravel, crushed stone and other coarse material used in concrete or as hardcore, in either case at least 50mm thick laid on at least 300µm (1200 gauge) polyethylene sheet with sealed joints, and itself laid on a bed of material which will not damage the sheet.

To prevent water collecting on the ground covering, either the top should be entirely above the highest level of the adjoining ground or, on sloping sites, consideration should be given to installing drainage on the outside of the up-slope side of the building (see Diagram 6).

b. Ventilated air space measuring at least 75mm from the ground covering to the underside of any wall-plates and at least 150mm to the underside of the suspended timber floor (or insulation if provided). Two opposing external walls should have ventilation openings placed so that the ventilating air will have a free path between opposite sides and to all parts. The openings should be not less than either 1,500mm ²/m run of external wall or 500mm²/m² of floor area, whichever gives the greater opening area. Any pipes needed to carry ventilating air should have a diameter of at least 100mm. Ventilation openings should incorporate suitable grilles which prevent the entry of vermin to the sub-floor but do not resist the air flow unduly. If floor levels need to be nearer to the ground to provide level access sub-floor ventilation can be provided through offset (periscope) ventilators.

see also the sections on DPCsDamp Proof Course - a strip of (usually) plastic built into walls to prevent damp rising or penetrating. see more

c. Damp-proof courses of impervious sheet material, engineering brick or slates in cement mortar or other material which will prevent the passage of moisture. Guidance for choice of materials is given in BS 5628:Part 3:2001.

d. In shrinkable clay soils, the depth of the air space may need to be increased to allow for heave.

4.15    In areas such as kitchens, utility rooms and bathrooms where water may be spilled, any board used as a flooring, irrespective of the storey[for the purposes of part B (fire) of the Approved Documents to the Building Regulations] this means a. any gallery[for the purposes of part B of the Approved Documents] - A raised area or platform around the sides or at the back of a room which provides extra space. Habitable room A room used, or intended to be used, for dwellinghouse[for the purposes of part B of the Approved Documents] - A unit of residential accommodation occupied (whether or not as a sole or main residence): a. by a single person or by people living together as a family b. by not more than six residents living together as a single household, including a household where care is provided for residents. (See also paragraphs 0.22 and 0.23.) Dwellinghouse does not include a flat or a building containing a flat. purposes (including; for the purposes of Part B, a kitchen, but not a bathroom). if its area is more than half that of the space into which it projects; and b. a roof, unless it is accessible only for maintenance and repair., should be moisture resistant. In the case of chipboard it should be of one of the grades with improved moisture resistance specified in BS 7331:1990 or BS EN 312 Part 5:1997. It should be laid, fixed and jointed in the manner recommended by the manufacturer To demonstrate compliance the identification marks should be facing upwards. Any softwood boarding should be at least 20mm thick and from a durable species or treated with a suitable preservative.

Alternative approach

4.16    The requirement can also be met (see paragraph 4.14 above) by following the relevant recommendations of Clause 11 of BS CP 102:1973.

SUSPENDED CONCRETE GROUND FLOORS (MOISTURE FROM THE GROUND)

4.17 Any suspended floor of in situ or precast concrete, including beamSubstantial, usually horizontal structural member. and block floors, next to the ground will meet the requirement if it will adequately prevent the passage of moisture to the upper surface and if the reinforcement is protected against moisture.

Technical solution

4.18    One solution for a suspended concrete floor could be:

a. in situ concretethis is concrete cast on site in its final position rather than being fabricated somewhere else at least 100mm thick (but thicker if the structural design requires) containing at least 300kg of cement for each m3 of concrete; or

b. precast concrete construction with or without infilling slabs; and

c. reinforcing steel protected by concrete cover of at least 40mm if the concrete is in situ and at least the thickness required for a moderate exposure if the concrete is precast.

4.19    A suspended concrete floor will meet the requirements if it incorporates:

a. a damp-proof membrane (if the ground below the floor has been excavated below the lowest level of the surrounding ground and will not be effectively drained); and

b. a ventilated air space. This should measure at least 150mm clear from the ground to the underside of the floor (or insulation if provided). Two opposing external walls should have ventilation openings placed so that the ventilating air will have a free path between opposite sides and to all parts of the floor void. The openings should be not less than either 1 500mm2/m run of external wall or 500mm2/m2 of floor area, whichever gives the greater opening area. Any pipes needed to carry ventilating air should have a diameter of at least 100mm. Ventilation openings should incorporate suitable grilles which prevent the entry of vermin to the sub-floor but do not resist the air flow unduly.

4.20    In localities where flooding is likely, consideration may be given to including means of inspecting and clearing out the sub-floor voids beneath suspended floors. For guidance, see the ODPM publication on preparing for floods.

GROUND FLOORS AND FLOORS EXPOSED FROM BELOW (RESISTANCE TO DAMAGE FROM INTERSTITIAL CONDENSATION)

4.21 A ground floor or floor exposed from below, i.e. above an open parking space or passageway, as shown in Diagram 7, will meet the requirement if it is designed and constructed in accordance with Clause 8.5 and Appendix D of BS 5250:2002, BS EN ISO 13788:2002 and BR 262.

FLOORS (RESISTANCE TO SURFACE CONDENSATION AND MOULD GROWTH)

4.22    A floor will meet the requirement if:

a. a ground floor is designed and constructed so that the thermal transmittance (U-value) does not exceed 0.7W/m2K at any point; and

b. in the case of all floors, the junctions between elements are designed in accordance with the recommendations in the report on robust construction details, or follow the guidance of BRE IP17/01 .

Section 5: Walls

5.1   This section gives guidance for four situations:

a. internal and external walls exposed to moisture from the ground (see paragraphs 5.4 to 5.6);

b. external walls exposed to precipitation from the outside, covering:

i. solid external walls (see paragraphs 5.8 to 5.11);

ii. cavity[for the purposes of part B of the Approved Documents] - A space enclosed by elements of a building (including a suspended ceiling) or contained within an element, but not a room, cupboard, circulation space, protected shaft or space within a fluepipe to conduct gas, typically ventilation air or boiler exhaust. see Flue, chute, duct, pipe or conduit. external walls (see paragraphs 5.12 to 5.15);

iii. framed external walls (see paragraph 5.17);

iv. cracking of walls (see paragraph 5.18);

v. impervious cladding systems (see paragraphs 5.19 to 5.28);

vi. the joint between window and door frames and external walls and door thresholds (see paragraphs 5.29 to 5.33);

c. the risk of interstitial condensation in any type of wall (see paragraphs 5.34 to 5.35);

d. the risk of surface condensation or mould growth on any type of wall (see paragraph 5.36).

A wall includes piers, columns and parapets. It also includes chimneys if they are attached to the building. It does not include windows, doors and similar openings, but does include the joint between their frames and the wall. In the following, the term ‘precipitation’ includes the effects of spray blown from the sea or any other body of water adjacent to the building.

5.2    Walls should:

a. resist the passage of moisture from the ground to the inside of the building; and

b. not be damaged by moisture from the ground and not carry moisture from the ground to any part which would be damaged by it, and, if the wall is an external wall:

c. resist the penetration of precipitation to components of the structure that might be damaged by moisture; and

d. resist the penetration of precipitation to the inside of the building; and

e. be designed and constructed so that their structural and thermal performance are not adversely affected by interstitial condensation; and

f. not promote surface condensation or mould growth, given reasonable occupancy conditions.

INTERNAL AND EXTERNAL WALLS (MOISTURE FROM THE GROUND)

5.4    Any internal or external wall will meet the requirement if a damp proof course is provided.

Technical solution

5.5    An internal or external wall will meet the requirement if it is built as follows (unless it is subject to groundwater pressure, in which case see the Alternative approach — paragraph 5.6):

a. damp-proof course of bituminous material, polyethylene, engineering bricks or slates in cement mortar or any other material that will prevent the passage of moisture. The damp proof course should be continuous with any damp-proof membrane in the floors; and

b. if the wall is an external wall, the damp-proof course should be at least 150mm above the level of the adjoining ground (see Diagram 8), unless the design is such that a part of the building will protect the wall; and

c. if the wall is an external cavity wall, (see Diagram 9a) the cavity should be taken down at least 225mm below the level of the lowest damp-proof course, or a damp-proof tray should be provided so as to prevent precipitation passing into the inner leaf (see Diagram 9b), with weep holes every 900mm to assist in the transfer of moisture through the external leaf. Where the damp-proof tray does not extend the full length of the exposed wall, i.e. above an opening, stop ends and at least two weep holes should be provided.

Alternative approach

5.6    The requirement can also be met by following the relevant recommendations of Clauses 4 and 5 of BS 8215:1991. BS 8102:1990 includes recommendations for walls subject to groundwater pressure including basement walls.

EXTERNAL WALLS (MOISTURE FROM THE OUTSIDE)

5.7    As well as giving protection against moisture from the ground, an external wall should give protection against precipitation. This protection can be given by a solid wall of sufficient thickness (see paragraphs 5.8 to 5.11), or by a cavity wall (see paragraphs 5.12 to 5.18), or by an impervious or weather-resisting cladding (see paragraphs 5.19 to 5.28).

SOLID EXTERNAL WALLS

5.8    Any solid wall will meet the requirement if it will hold moisture arising from rain and snow until it can be released in a dry period without penetrating to the inside of the building, or causing damage to the building. The wall thickness will depend on the type of brick and block and on the severity of wind-driven rain. A method of describing the exposure to wind-driven rain is given in BS 8104:1992; see also BS 56283:2001.

Technical solution

5.9    A solid external wall in conditions of very severe exposure should be protected by external impervious cladding, but in conditions of severe exposure may be built as follows:

a. brickwork or stonework at least 328mm thick, dense aggregate concrete blockwork at least 250mm thick, or lightweight aggregate or aerated autoclaved concrete blockwork at least 215mm thick; and

b. rendering: the exposed face of the bricks or blocks should be rendered or be given no less protection. Rendering should be in two coats with a total thickness of at least 20mm and should have a scraped or textured finish. The strength of the mortar should be compatible with the strength of the bricks or blocks. The joints, if the wall is to be rendered, should be raked out to a depth of at least 10mm. Further guidance is given in BS EN 998:2003. The rendering mix should be one part of cement, one part of lime and six parts of well graded sharp sand (nominal mix 1:1:6) unless the blocks are of dense concrete aggregate, in which case the mix may be 1:0.5:4. BS 5262:1991 includes recommendations for a wider range of mixes according to the severity of exposure and the type of brick or block.

Premixed and proprietary renders should be used in accordance with the manufacturer’s instructions;

c. protection should be provided where the top of walls, etc. would otherwise be unprotected (see Diagram 10). Unless the protection and joints will be a complete barrier to moisture, a damp-proof course should also be provided;

d. damp-proof courses, cavity trays and closers should be provided and designed to ensure that water drains outwards:

i. where the downward flow will be interrupted by an obstruction, such as some types of lintel; and

ii. under openings, unless there is a sill and the sill and its joints will form a complete barrier; and

iii. at abutments between walls and roofs.

5.10    Insulation. A solid external wall may be insulated on the inside or on the outside. Where it is on the inside a cavity should be provided to give a break in the path for moisture and where it is on the outside it should provide some resistance to the ingress of moisture to ensure the wall remains relatively dry (see Diagram 11).

Alternative approach

5.11    The requirement can also be met by following the relevant recommendations of BS 5628-3:2001 The code describes alternative constructions to suit the severity of the exposure and the type of brick or block.

CAVITY EXTERNAL WALLS

5.12    Any external cavity wall will meet the requirement if the outer leaf is separated from the inner leaf by a drained air space, or in any other way which will prevent precipitation from being carried to the inner leaf.

Technical solution

5.13    The construction of a cavity external wall could include:

a. outer leaf masonry (bricks, blocks, stone or manufactured stone); and

b. cavity at least 50mm wide. The cavity is to be bridged only by wall ties, cavity trays provided to prevent moisture being carried to the inner leaf (see paragraph 5.15 for cavity insulation), and cavity barriers, firestops and cavity closures, where appropriate; and

c. inner leaf masonry or frame with lining.

Masonry units should be laid on a full bed of mortar with the cross joints substantially and continuously filled to ensure structural robustness and weather resistance.

Where a cavity is to be partially filled, the residual cavity should not be less than 50mm wide (see Diagram 11).

Alternative approach

5.14    The requirement can also be met by following the relevant recommendations of BS 5628-3:2001. The code describes factors affecting rain penetration of cavity walls.

CAVITY INSULATION

5.15    A full or partial fill insulating material may be placed in the cavity between the outer leaf and an inner leaf of masonry subject to the following conditions:

a. The suitability of a wall for installing insulation into the cavity should be determined either by reference to the map in Diagram 12 and the associated Table 4 or following the calculation or assessment procedure in current British or CEN standards. When partial fill materials are to be used, the residual cavity should not be less than 50mm nominal; and

b. A rigid (board or baff) thermal insulating material built into the wall should be the subject of current certification from an appropriate body or a European Technical ApprovalA favourable technical assessment of the fitness for use of a construction product for an intended use, issued for the purposes of the Construction Products Directive by a body authorised by a Member State to issue European Technical Approvals for those purposes and notified by that Member State to the European Commission. and the work should be carried out in accordance with the requirements of that document; or

c. Other insulating materials inserted into the cavity after the wall has been constructed should have certification from an appropriate body and be installed in accordance with the appropriate installations code. The suitability of the wall for filling is to be assessed before the work is carried out and the person undertaking the work should operate under an Approved Installer Scheme that includes an assessment of capability. Alternatively the insulating material should be the subject of current certification from an appropriate body or a European Technical Approval and the work should be carried out in accordance with the requirements of that document by operatives either directly employed by the holder of the document or employed by an installer approved to operate under the document; or

d. Urea-formaldehyde foam inserted into the cavity should be in accordance with BS 5617:1985 and be installed in accordance with BS 561 8:1985. The suitability of the wall for foam filling is to be assessed before the work is carried out and the person undertaking the work should operate under an Approved Installer Scheme that includes an assessment of capability.

e. When the cavity of an existing house is being filled, special attention should be given to the condition of the external leaf of the wall, e.g. its state of repair and type of pointing. Guidance is given in BS 82O8-1 :1985. Some materials that are used to fill existing cavity walls may have a low risk of moisture being carried over to the internal leaf of the wall. In cases where a third party assessment of such a cavity fill material contains a method of assessing the construction of the walls and exposure risk, the procedure set out below may be replaced by that method.

These diagrams below are becoming rather misleading as insulation values increase and we approach 2016 when zero carbon construction is introduced. The thickness of insulation will probably need to be at least 125mm and possibly up to 300mm, depending on the type of construction.

As insulation thicknesses increase, (and hence overall wall thickness) it is likely that rain screensthis is a (usually thin) outer cladding on a wall which prevents rain, snow, etc getting at the structure of the wall behind. see more on rain screens will become more common as a form of external cladding. These are not shown here although the ‘Timber framed wall[for the purposes of part C of the Approved Documents] - A partition consisting of board or boards connected to both sides of a wood or metal frame. with tile cladding’ approximates to it. See 5.21 below

5.16    If the map given in Diagram 12 is used, determine the national exposure and, where appropriate, apply the following modifiers:

i. where local conditions accentuate wind effects, such as open hillsides or valleys where the wind is funnelled onto the wall, add one to this exposure zone value;

ii. where walls do not face into the prevailing wind, subtract one from this exposure zone value.

(The national exposure zone value can be more accurately calculated from the larger scale maps and correction factors given in BS 8104:1 992).

Determine the recommended constructions from the modified exposure zone values given in Table 4. Further guidance as to the use of this table is given in BRE Report 262.

5.17    Any framed external wall will meet the requirement if the cladding is separated from the insulation or sheathing by a vented and drained cavity with a membrane that is vapour open, but resists the passage of liquid water, on the inside of the cavity (see Diagram 11).

5.18    Severe rain penetration may occur through cracks in masonry external walls caused by thermal movement in hot weather or subsidence after prolonged droughts. The possibility of this should be taken into account when designing a building. Detailed guidance is given in:

a. BRE Building Elements: Walls, windows and door; and

b. BRE Report 292;

c. Guidance for choice of materials is given in BS5628-3:2001

IMPERVIOUS CLADDING SYSTEMS FOR WALLS

5.19    Cladding systems for walls should:

a. resist the penetration of precipitation to the inside of the building; and

b. not be damaged by precipitation and not carry precipitation to any part of the building which would be damaged by it.

5.20    Cladding can be designed to protect a building from precipitation (often driven by the wind) either by holding it at the face of the building or by stopping it from penetrating beyond the back of the cladding.

see more on moisture resisting timber and using timber as a cladding

5.21    Any cladding will meet the requirement if:

a. it is jointless or has sealed joints, and is impervious to moisture (so that moisture will not enter the cladding); or

b. it has overlapping dry joints, is impervious or weather resisting, and is backed by a material which will direct precipitation which enters the cladding towards the outer face.

5.22    Some materials can deteriorate rapidly without special care and they should only be used as the weather-resisting part of a cladding system if certain conditions are met (see Approved Document supporting Regulation 7, Materials and workmanship). The weather-resisting part of a cladding system does not include paint nor does it include any coating, surfacing or rendering which will not itself provide all the weather resistance.

Technical solution

5.23    Cladding may be:

a. impervious including metal, plastic, glass and bituminous products; or

b. weather resisting including natural stone or slate, cement based products, fired clay and wood; or

c. moisture resisting including bituminous and plastic products lapped at the joints, if used as a sheet material, and permeable to water vapour unless there is a ventilated space directly behind the material; or

d. jointless materials and sealed joints, which would allow for structural and thermal movement.

5.24    Dry joints between cladding units should be designed so that precipitation will not pass through them, or the cladding should be designed so that precipitation which enters the joints will be directed towards the exposed face without it penetrating beyond the back of the cladding. Note: Whether dry joints are suitable will depend on the design of the joint or the design of the cladding and the severity of the exposure to wind and rain.

5.25    Each sheet, tile and section of cladding should be securely fixed. Guidance as to appropriate fixing methods is given in BS 8000- 6:1990. Particular care should be taken with detailing and workmanship at the junctions between cladding and window and door openings as they are vulnerable to moisture ingress.

5.26    Insulation can be incorporated into the construction provided it is either protected from moisture or unaffected by it.

5.27    Where cladding is supported by timber components or is on the façade of a timber framed building, the space between the cladding and the building should be ventilated to ensure rapid drying of any water that penetrates the cladding.

Alternative approach

5.28     The requirement can also be met by following the relevant recommendations of:

a. BS CP 143 for sheet roof and wall coverings made from the following materials:

Part 1:1958 Corrugated and troughed aluminium

Part 5:1964 Zinc

Part 10:1973 Galvanised corrugated steel

Part 12:1970 (1988) Copper

Part 15:1973 (1986) Aluminium

Part 16:1974 Semi-rigid asbestos bitumen sheets

Recommendations for lead are included in BS 691 5:2001;

b. BS 8219:2001;

c. BS 8200:1985;

d. BS 8297:2000;

e. BS 8298:1994;

f. MCRMA Technical Paper 6;

g. MCRMA Technical Paper 9.

These documents describe the materials and contain design considerations including recommendations for fixing.

JOINT BETWEEN DOORS AND WINDOWS

5.29    The joint between walls and door and window frames should:

a. resist the penetration of precipitation to the inside of the building; and

b. not be damaged by precipitation and not permit precipitation to reach any part of the building which would be damaged by it.

5.30    Damp-proof courses should be provided to direct moisture towards the outside:

a. where the downward flow of moisture would be interrupted at an obstruction, e.g. at a lintel;

b. where sill elements, including joints, do not form a complete barrier to the transfer of precipitation, e.g. under openings, windows and doors;

c. where reveal elements, including joints, do not form a complete barrier to the transfer of rain and snow, e.g. at openings, windows and doors.

5.31    In some cases the width of the cavity due to thermal insulation and the 50mm clearance for drainage may be such that the window frame is not wide enough to completely cover the cavity closer. The reveal may need to be lined with plasterboard, dry lining, a support system or a thermal backing board. Direct plastering of the internal reveal should only be used with a backing of expanded metal lathing or similar.

5.32    In areas of the country in driving rain exposure zone 4 checked rebates should be used in all window and door reveals. The frame should be set back behind the outer leaf of masonry, which should overlap it as shown in Diagram 13. Alternatively an insulated finned cavity closer may be used.

see also Disabled access

DOOR THRESHOLDS

5.33    Where an accessible threshold is provided to allow unimpeded access, as specified in Part M, Access to and use of buildings, it will meet the requirements if:

a. the external landingA platform or part of floor structure at the end of a flight of stairs or ramp. (Diagram 14) is laid to a fall between 1 in 40 and 1 in 60 in a single direction away from the doorway;

b. the sill leading up to the door threshold has a maximum slope of 15°.

Further advice for the development of accessible thresholds is given in BRE GBG 47 and the TSO document.

EXTERNAL WALLS (RESISTANCE TO DAMAGE FROM INTERSTITIAL CONDENSATION)

see more about interstitial condensation

5.34    An external wall will meet the requirement if it is designed and constructed in accordance with Clause 8.3 of BS 5250:2002, and BS EN ISO 13788:2001

EXTERNAL WALLS (RESISTANCE TO SURFACE CONDENSATION AND MOULD GROWTH)

With increasing levels of insulation, surface condensation should cease being a problem except possibly in areas of very high humidity such as bathrooms where condensation can occur intermittently. The only answer here is to use completely non absorbent surface materials.

5.36    An external wall will meet the requirement if:

a. it is designed and constructed so that the thermal transmittance (U-value) does not exceed 0.7W/m2K at any point; and

b. the junctions between elements and details of openings, such as doors and windows, are designed in accordance with the recommendations in the report on robust construction details, or follow the guidance of BRE IP17/01.

Section 6: Roofs

6.1    This section gives guidance for three situations:

a. roofs exposed to precipitation from the outside (see paragraphs 6.3 to 6.9);

b. the risk of interstitial condensation in roofs (see paragraphs 6.10 to 6.13);

c. the risk of condensation or mould growth on the internal surface of roofs (see paragraph 6.14).

6.2    Roofs should:

a. resist the penetration of precipitation to the inside of the building; and

b. not be damaged by precipitation and not carry precipitation to any part of the building which would be damaged by it;

c. be designed and constructed so that their structural and thermal performance are not adversely affected by interstitial condensation.

ROOFS (RESISTANCE TO MOISTURE FROM THE OUTSIDE)

see more on roofs

6.3    Roofing can be designed to protect a building from precipitation either by holding the precipitation at the face of the roof or by stopping it from penetrating beyond the back of the roofing system.

6.4     Any roof will meet the requirement if:

a. it is jointless or has sealed joints, and is impervious to moisture (so that moisture will not enter the roofing system); or

b. it has overlapping dry joints, is impervious or weather resisting, and is backed by a material which will direct precipitation which enters the roof towards the outer face (as with roofing felt).

6.5    Some materials can deteriorate rapidly without special care and they should only be used as the weather-resisting part of a roof if certain conditions are met (see Approved Document supporting Regulation 7, Materials and workmanship 133). The weather-resisting part of a roofing system does not include paint nor does it include any coating, surfacing or rendering which will not itself provide all the weather resistance.

Technical solution

6.6    Roofing systems may be:

a. impervious including metal, plastic and bituminous products; or

b. weather resisting including natural stone or slate, cement based products, fired clay and wood; or

c. moisture resisting including bituminous and plastic products lapped at the joints, if used as a sheet material, and permeable to water vapour unless there is a ventilated space directly behind the material; or

d. jointless materials and sealed joints, which would allow for structural and thermal movement.

6.7    Dry joints between roofing sheets should be designed so that precipitation will not pass through them, or the system should be designed so that precipitation which enters the joints will be drained away without penetrating beyond the back of the roofing system. Note: Whether dry joints are suitable will depend on the design of the joint or the design of the roofing system and the severity of the exposure to wind and rain.

6.8    Each sheet, tile and section of roof should be fixed in an appropriate manner. Guidance as to appropriate fixing methods is given in BS 8000-6:1990.

Alternative approach

6.9    The requirement can also be met by following the relevant recommendations of:

a. BS CP 143 for sheet roof and wall coverings made from the following materials:

Part 1:1958 Corrugated and troughed aluminium

Part 5:1964 Zinc

Part 10:1973 Galvanized corrugated steel

Part 12:1970 (1988) Copper

Part 15:1973 (1986) Aluminium

Part 16:1974 Semi-rigid asbestos bitumen sheets.

Recommendations for lead are included in BS 691 5:2001;

b. BS 8219:2001;

c. BS 8200:1985;

d. MCRMA Technical Paper 6;

e. MCRMA Technical Paper 9.

These documents describe the materials and contain design considerations including recommendations for fixing.

ROOFS (RESISTANCE TO DAMAGE FROM INTERSTITIAL CONDENSATION)

6.10    A roof will meet the requirement if it is designed and constructed in accordance with Clause 8.4 of BS 5250:2002 and BS EN ISO 13788:2002. Further guidance is given in the BRE Report BR 262.

6.11    The requirement will be met by the ventilation of cold deck roofs, i.e. those roofs where the moisture from the building can permeate the insulation. For the purposes of health and safety it may not always be necessary to provide ventilation to small roofs such as those over porches and bay windows. Although a part of a roof which has a pitch of 70° or more is to be insulated as though it were a wall, the provisions in this document apply to roofs of any pitch.

6.12    To avoid excessive moisture transfer to roof voids gaps and penetrations for pipes and electrical wiring should be filled and sealed; this is particularly important in areas of high humidity, e.g. bathrooms and kitchens. An effective draught seal should be provided to loft hatches to reduce inflow of warm air and moisture.

6.13    Because of the high internal temperatures and humidities, there is a particular risk of interstitial condensation in the roofs of swimming pools and other buildings in which high levels of moisture are generated; specialist advice should be sought when these are being designed.

ROOFS (RESISTANCE TO SURFACE CONDENSATION AND MOULD GROWTH)

6.14   A roof will meet the requirement if:

a. it is designed and constructed so that the thermal transmittance (U-value) does not exceed 0.35W/m2K at any point; and

b. the junctions between elements and the details of openings, such as windows, are designed in accordance with the recommendations in the report on robust construction details, or follow the guidance of BRE 1P17/01 or MCRMA Paper 14 for profiled metal roofing.

Annex A: Guidance on the assessment of land affected by contaminants

downloadable from the Environment Agency publications catalog

A.1 A substantial amount of guidance on the assessment of contaminated land has been published to support the implementation of Part IIA of the Environmental Protection Act 1991. Most of this guidance is contained in the joint Defra/Environment Agency Contaminated Land Research Reports (CLRs). This guidance can be used to support the assessment process set out in Section 2. A summary of the reports is set out below and an outline of the process is given in Figure A1

A.2 For health, risk estimation can be carried out using generic assessment criteria such as contaminant soil guideline values (SGVsSoil Guidance Values) or relevant and appropriate environmental standards. SGVs represent contaminant concentrations which may pose unacceptable risks to health. The development of SGVs for a range of priority contaminants is described in the Defra/Environment Agency reports CLR 7, CLR 8, CLR 9 and CLR 10.

A.3 CLR 10 describes the Contaminated Land Exposure Assessment Model (CLEAContaminated Land Exposure Assessment Model) for deriving SGVs for three different site uses: (i) residential, (ii) residential with plant uptake and (iii) commercial/industrial. In this way the relative importance of each of the pollutant linkages is considered. For example, for residential site use it is assumed residents have private gardens and/ or access to community open space close to the home and that some may use their gardens to grow vegetables. CLR 10 gives details of the conceptual model underpinning each of the standard land uses.

A.4 A series of Defra/Environment Agency SGVSoil Guidance Value reports contain SGVs for a range of contaminants, one report for each contaminant, and the corresponding TOX reports contain the toxicological data used to derive the SGVs. SGVs should be used only in conjunction with the CLR 7 to 10 reports and associated SGV and TOX reports.

A.5 The use of ICRCL (Interdepartmental Committee on the Redevelopment of Contaminated Land) document Guidance Note 59/83: Guidance on the assessment and redevelopment of contaminated land is no longer appropriate in health risk assessment and has been withdrawn by Defra.

Available to download from the Environment Agency

A.6 CLR 7 provides advice regarding such issues. In certain cases the most appropriate action may be to redesign the building layout. Further guidance can be obtained from the Environment Agency/NHBC R & D Publication 66.

A.7 An alternative to the generic approach is to undertake a more site-specific quantitative risk assessment using the principles of risk assessment or a risk assessment model. Specialist advice should be sought.

Section 1: Fire detection and fire alarm systems

Introduction.

1.1 Provisions are made in this section for suitable arrangements to be made in dwellinghouses to give early warning in the event of fire.

General

1.2 The installation of smoke alarms, or automatic fire detection and alarm systems can significantly increase the level of safety by automatically giving an early warning of fire. The following guidance is appropriate for most dwellinghouses. However, where it is known that the occupants of a proposed dwellinghouse[for the purposes of part B of the Approved Documents] - A unit of residential accommodation occupied (whether or not as a sole or main residence): a. by a single person or by people living together as a family b. by not more than six residents living together as a single household, including a household where care is provided for residents. (See also paragraphs 0.22 and 0.23.) Dwellinghouse does not include a flat or a building containing a flat. are at a special risk from fire, it may be more appropriate to provide a higher standard of protection, e.g. additional detectors.

1.3 All new dwellinghouses should be provided with a fire detection and fire alarm system in accordance with the relevant recommendations of BSBritish Standard 5839-6:2004 to at least a Grade D Category standard.

1.4 The smoke and heat alarms should be mains-operated and conform to BS 5446-1:2000 or BS 5446-2:2003, respectively: Fire detection and fire alarm devices for dwellinghouses, Part 1 Specification for smoke alarms; or Part 2 Specification for heat alarms. They should have a standby power supply, such as a battery (either rechargeable or non-rechargeable) or capacitor.

Note: BS 5446-1 covers smoke alarms based on ionization chamber smoke detectors and optical (photo-electric) smoke detectors. The different types of detector respond differently to smouldering and fast-flaming fires. Either type of detector is generally suitable. However, the choice of detector type should, if possible, take into account the type of fire that might be expected and the need to avoid false alarms. Optical detectors tend to be less affected by low levels of ‘invisible’ particles, such as fumes from kitchens, that often cause false alarms. Accordingly, they are generally more suitable than ionization chamber detectors for installation in circulation spaces adjacent to kitchens.

Large houses

There is a useful explanation of Grade Categories on the FIAFire Industry Association site. On the subject of fire alarms there is evidence of a fairly large percentage of them being deliberately disconnected to avoid nuisance triggering. Interest has been growing in sprinkler systems due to their high reliability and efficacy. Wales is considering making them mandatory in all new housebuilding. 

1.5 A dwellinghouse is regarded as large if it has more than one storey[for the purposes of part B (fire) of the Approved Documents to the Building Regulations] this means a. any gallery[for the purposes of part B of the Approved Documents] - A raised area or platform around the sides or at the back of a room which provides extra space. Habitable room A room used, or intended to be used, for dwellinghouse purposes (including; for the purposes of Part B, a kitchen, but not a bathroom). if its area is more than half that of the space into which it projects; and b. a roof, unless it is accessible only for maintenance and repair. and any of those storeys exceed 200m².

1.6 A large dwellinghouse of 2 storeys (excluding basement storeys) should be fitted with a fire detection and fire alarm system of Grade B category LD3 as described in BS 5839-6:2004.

1.7 A large dwellinghouse of 3 or more storeys (excluding basement storeys) should be fitted with a Grade A Category LD2 system as described in BS 5839-6:2004, with detectors sited in accordance with the recommendations of BS 5839-1:2002 for a Category L2 system.

Material alterations

1.8 Where new habitable rooms are provided above the ground floor level, or where they are provided at ground floor level and there is no final exit[for the purposes of part B of the Approved Documents] - The termination of an escape route[for the purposes of part B of the Approved Documents] - Route forming that part of the means of escape from any point in a building to a final exit. from a building giving direct access to a street, passageway, walkway or open space, and sited to ensure the rapid dispersal of persons from the vicinity of a building so that they are no longer in danger from fire and/or smoke. Note: Windows are not acceptable as final exits. from the new room, a fire detection and fire alarm system should be installed. Smoke alarms should be provided in the circulation spaces of the dwellinghouse in accordance with paragraphs 1.10 to 1.18 to ensure that any occupants of the new rooms are warned of any fire that may impede their escape.

Positioning of smoke and heat alarms

1.10 Detailed guidance on the design and installation of fire detection and alarm systems in dwellinghouses is given in BS 5839-6:2004. However, the following guidance is appropriate to most common situations.

1.11 Smoke alarms should normally be positioned in the circulation spaces between sleeping spaces and places where fires are most likely to start (e.g. kitchens and living rooms) to pick up smoke in the early stages of a fire.

1.12 There should be at least one smoke alarm[for the purposes of part B of the Approved Documents] - A device containing within one housing all the components, except possibly the energy source, necessary for detecting smoke and giving an audible alarm. on every storey of a dwellinghouse.

1.13 Where the kitchen area is not separated from the stairway or circulation space[for the purposes of part B of the Approved Documents] A space (including a protected stairway) mainly used as a means of access between a room and an exit from the building or compartment[for the purposes of part B of the Approved Documents] - (fire) A building or part of a building, comprising one or more rooms, spaces or storeys, constructed to prevent the spread of fire to or from another part of the same building, or an adjoining building. (A roof space above the top storey of a compartment is included in that compartment.) (See also ‘Separated part’.) by a door, there should be a compatible interlinked heat detector or heat alarm in the kitchen, in addition to whatever smoke alarms are needed in the circulation space(s).

1.14 Where more than one alarm is installed they should be linked so that the detection of smoke or heat by one unit operates the alarm signal in all of them. The manufacturers’ instructions about the maximum number of units that can be linked should be observed.

1.15 Smoke alarms/detectors should be sited so that:

a. there is a smoke alarm in the circulation space within 7.5m of the door to every habitable room;

b. they are ceiling[for the purposes of part B of the Approved Documents] - A part of a building which encloses and is exposed overhead in a room, protected shaft or circulation space. (The soffit of a rooflight is included as part of the surface of the ceiling, but not the frame. An upstand below a rooflight would be considered as a wall.)-mounted and at least 300mm from walls and light fittings (unless, in the case of light fittings, there is test evidence to prove that the proximity of the light fitting will not adversely affect the efficiency of the detector). Units designed for wall-mounting may also be used provided that the units are above the level of doorways opening into the space and they are fixed in accordance with manufacturers’ instructions; and

c. the sensor in ceiling-mounted devices is between 25mm and 600mm below the ceiling (25-150mm in the case of heat detectors or heat alarms).

Note: This guidance applies to ceilings that are predominantly flat and horizontal.

1.16 It should be possible to reach the smoke alarms to carry out routine maintenance, such as testing and cleaning, easily and safely. For this reason smoke alarms should not be fixed over a stair or any other opening between floors.

1.17 Smoke alarms should not be fixed next to or directly above heaters or air-conditioning outlets. They should not be fixed in bathrooms, showers, cooking areas or garages, or any other place where steam, condensation or fumes could give false alarms.

1.18 Smoke alarms should not be fitted in places that get very hot (such as a boiler room) or very cold (such as an unheated porch).

They should not be fixed to surfaces which are normally much warmer or colder than the rest of the space, because the temperature difference might create air currents which move smoke away from the unit.

Power supplies

See electric  wiring diagram in part P of the regulations. It makes sense to plan fire alarm circuits to tie in with service ducts

1.19 The power supply for a smoke alarm system should be derived from the dwellinghouse’s mains electricity supply. The mains supply to the smoke alarm(s) should comprise a single independent circuit at the dwellinghouse’s main distribution board (consumer unit) or a single regularly used local lighting circuit. This has the advantage that the circuit is unlikely to be disconnected for any prolonged period. There should be a means of isolating power to the smoke alarms without isolating the lighting.

1.20 The electrical installation should comply with Approved DocumentThese are a part of the Building Regulations which ensure, if you follow them, that your plans will be automatically approved. The full set of the documents is available here P (Electrical safety).

1.21 Any cable suitable for domestic wiring may be used for the power supply and interconnection to smoke alarm systems. It does not need any particular fire survival properties except in large houses (BS 5839-6:2004 specifies fire resisting cables for Grade A and B systems). Any conductors used for interconnecting alarms (signalling) should be readily distinguishable from those supplying mains power, e.g. by colour coding.

Note: Mains-powered smoke alarms may be interconnected using radio-links, provided that this does not reduce the lifetime or duration of any standby power supply below 72 hours. In this case, the smoke alarms may be connected to separate power circuits (see paragraph 1.19)

1.22  Other effective options exist and are described in BS 5839-1:2002 and BS 5839-6:2004. For example, the mains supply may be reduced to extra low voltage in a control unit incorporating a standby trickle-charged battery, before being distributed at that voltage to the alarms.

Design and installation of systems

1.23  It is essential that fire detection and fire alarm systems are properly designed, installed and maintained. Where a fire alarm system is installed, an installation and commissioning certificate should be provided. Third party certification schemes for fire protection products and related services are an effective means of providing the fullest possible assurances, offering a level of quality, reliability and safety.

1.24  A requirement for maintenance cannot be made as a condition of passing plans by the Building Control Body[for the purposes of part B of the Approved Documents] - A term used to include both Local Authority Building Control and Approved Inspectors.. However, the attention of developers and builders is drawn to the importance of providing the occupants with information on the use of the equipment, and on its maintenance (or guidance on suitable maintenance contractors). See paragraph 0.11.

Note: BS 5839-1 and BS 5839-6 recommend that occupiers should receive the manufacturers’ instructions concerning the operation and maintenance of the alarm system.

Section 2: Means of escape

Introduction

In this section (B2) a room is defined as “An enclosed space within a building that is not used solely as a circulation space. (The term includes not only conventional rooms, but also walk-in cupboards that are not fittings, and large spaces such as warehouses and auditoria. The term does not include voids such as ducts, ceiling voids and roof spaces.)

A flat is defined as “A separate and self-contained premises constructed or adapted for use for residential purposes and forming part of a building from some other part of which it is divided horizontally”

2.1 The means of escape[for the purposes of part B of the Approved Documents] - Structural means whereby [in the event of fire] a safe route or routes is or are provided for persons to travel from any point in a building to a place of safety. from a typical one or two storey dwellinghouse is relatively simple to provide. Few provisions are specified in this document beyond ensuring that means are provided for giving early warning in the event of fire (see Section 1) and that suitable means are provided for emergency egress from each storey via windows or doors. With increasing height more complex provisions are needed because emergency egress through upper windows becomes increasingly hazardous. It is then necessary to protect the internal stairway. If there are floors more than 7.5m above ground level, the risk that the stairway will become impassable before occupants of the upper parts of the dwellinghouse have escaped is appreciable, and an alternative route from those parts should be provided. See Diagram 1.

Note: Ground level is explained in Appendix C, Diagram C1.

2.2 In providing any kind of fire protection in houses it should be recognised that measures which significantly interfere with the day-to-day convenience of the occupants may be less reliable in the long term.

Provisions for escape from the ground storey

2.3 Except for kitchens, all habitable rooms in the ground storey should either:

a. open directly onto a hall leading to the entrance or other suitable exit; or

b. be provided with a window (or door) which complies with paragraph 2.8.

Note: See also General Provisions.

Provisions for escape from upper floors not more than 4.5m above ground level

see the sections on stair design and spiral stairs. Particularly with refurb and extension work, the layout of rooms for escape in the event of fire can strongly influence the layout of staircases, lifts and service ducts.

2.4 Except for kitchens, all habitable rooms in the upper storey(s) of a dwellinghouse served by only one stair should be provided with:

a. a window (or external door) which complies with paragraph 2.8; or

b. direct access to a protected stairway[for the purposes of part B of the Approved Documents] - A stair discharging through a final exit to a place of safety (including any exit passageway between the foot of the stair and the final exit) that is adequately enclosed with fire-resisting[for the purposes of part B of the Approved Documents] - The ability of a component or construction of a building to satisfy, for a stated period of time, some or all of the appropriate criteria specified in the relevant part of BS 476 construction. (as described in 2.6 (a) or (b)).

Note: A single window can be accepted to serve two rooms provided both rooms have their own access to the stairs. A communicating door between the rooms should also be provided so that it is possible to gain access to the window without passing through the stair enclosure.

Note: See also General Provisions.

Provisions for escape from upper floors more than 4.5m above ground level

2.5 The provisions described in 2.6 and 2.7 need not be followed if the dwelling house has more than one internal stairway, which afford effective alternative means of escape and are physically separated from each other.

Note: The necessary degree of separation is a matter of judgement, eg. stairs may be separated by fire-resisting construction or by a number of rooms.

Dwellinghouses with one floor more than 4.5m above ground level

2.6 The dwellinghouse may either have a protected stairway as described in (a) below, or the top floor can be separated and given its own alternative escape route[for the purposes of part B of the Approved Documents] - Escape routes sufficiently separated by either direction and space, or by fire-resisting construction, to ensure that one is still available should the other be affected by fire. Note: A second stair, balcony or flat roof which enables a person to reach a place free from danger from fire, is considered an alternative escape route for the purposes of a dwellinghouse. as described in (b).

a. The upper storeys (those above ground storey) should be served by a protected stairway (protected at all levels) which should either:

i. extend to a final exit, see Diagram 2(a); or

ii. give access to at least two escape routes at ground level, each delivering to final exits and separated from each other by fire-resisting construction and fire doors, see Diagram 2(b); or

b. The top storey should be separated from the lower storeys by fire-resisting construction and be provided with an alternative escape route leading to its own final exit. See Diagram 3.

Note: See also General Provisions.

Dwellinghouses with more than one floor over 4.5m above ground level

2.7 Where a dwellinghouse has two or more storeys with floors more than 4.5m above ground level (typically a dwellinghouse of four or more storeys) then, in addition to meeting the provisions in paragraph 2.6:

a. an alternative escape route should be provided from each storey or level situated 7.5m or more above ground level. Where the access to the alternative escape route is via:

i. the protected stairway to an upper storey; or

ii. a landingA platform or part of floor structure at the end of a flight of stairs or ramp. within the protected stairway enclosure to an alternative escape route on the same storey; then

iii. the protected stairway at or about 7.5m above ground level should be separated from the lower storeys or levels by fire resisting construction, see Diagram 3; or

see more on sprinkler systems.

b. the dwellinghouse should be fitted throughout with a sprinkler system designed and installed in accordance with BS 9251:2005.

Note: See also General Provisions.

General provisions

Emergency egress windows and external doors

2.8 Any window provided for emergency egress purposes and any external door provided for escape should comply with the following conditions:

a. the window should have an unobstructed openable area that is at least 0.33m² and at least 450mm high and 450mm wide (the route through the window may be at an angle rather than straight through). The bottom of the openable area should be not more than 1100mm above the floor; and

note that in the whole of this document a building is “any permanent or temporary building but not any other kind of structure or erection. A reference to a building includes a reference to part of a building”.

b. the window or door should enable the person escaping to reach a place free from danger from fire. This is a matter for judgement in each case, but, in general, a courtyard or back garden from which there is no exit other than through other buildings would have to be at least as deep as the dwellinghouse is high to be acceptable, see Diagram 4.

Note 1: Approved Document K Protection from falling, collision and impact specifies a minimum guarding height of 800mm, except in the case of a window in a roof where the bottom of the opening may be 600mm above the floor.

Note 2: Locks (with or without removable keys) and stays may be fitted to egress windows, subject to the stay being fitted with a release catch, which may be child resistant.

see more on Roof Lights

Note 3: Windows should be designed such that they will remain in the open position without needing to be held by a person making their escape.

Inner rooms

2.9 A room whose only escape route is through another room is termed an inner room[for the purposes of part B of the Approved Documents] - Room from which escape is possible only by passing through another room (the access room[for the purposes of part B of the Approved Documents] - A room through which the only escape route from an inner room passes.). and is at risk if a fire starts in that other room (access room). This situation may arise with open-plan layouts and galleries. Such an arrangement is only acceptable where the inner room is:

a. a kitchen;

b. a laundry or utility room;

c. a dressing room;

d. a bathroom, WC, or shower room;

e. any other room on a floor, not more than 4.5m above ground level, provided with an emergency egress window which complies with paragraph 2.8; or

f. a gallery which complies with paragraph 2.12.

Note: A room accessed only via an inner room (an inner-inner room) may be acceptable if it complies with the above, not more than one door separates the room from an interlinked smoke alarm and none of the access rooms is a kitchen.

see more on roof design. The increasing use of living roofsA roof with a covering of soil or growing medium and plants. They tend to be divided into turf roofs with a 150mm layer of soil and sedum roofs with a thinner layer (about 40mm). see Living RoofsA roof with a covering of soil or growing medium and plants. They tend to be divided into turf roofs with a 150mm layer of soil and sedum roofs with a thinner layer (about 40mm). see Living Roofs for recreation may, at the design stage, coincide with the need for escape from upper storeys.

Balconies and flat roofs

2.10 A flat roof forming part of a means of escape should comply with the following provisions:

a. the roof should be part of the same building from which escape is being made;

b. the route across the roof should lead to a storey exit[for the purposes of part B of the Approved Documents] - A final exit, or a doorway giving direct access into a protected stairway, firefighting lobby or external escape route. or external escape route; and

c. the part of the roof forming the escape route and its supporting structure, together with any opening within 3m of the escape route, should provide 30 minutes fire resistance[for the purposes of part B of the Approved Documents] - The ability of a component or construction of a building to satisfy, for a stated period of time, some or all of the appropriate criteria specified in the relevant part of BS 476. (see Appendix A, Table Al).

see more on balconies

2.11 Where a balcony or flat roof is provided for escape purposes guarding may be needed, in which case it should meet the provisions in Approved Document K Protection from falling, collision and impact.

Galleries

2.12 A gallery should be provided with an alternative exit[for the purposes of part B of the Approved Documents] - One of two or more exits, each of which is separate from the other. or, where the gallery floor is not more than 4.5m above ground level, an emergency egress window which complies with paragraph 2.8. Alternatively, where the gallery floor is not provided with an alternative exit or escape window, it should comply with the following;

a. the gallery should overlook at least 50% of the room below (see Diagram 5);

b. the distance between the foot of the access stair to the gallery and the door to the room containing the gallery should not exceed 3m;

c. the distance from the head of the access stair to any point on the gallery should not exceed 7.5m; and

d. any cooking facilities within a room containing a gallery should either:

i. be enclosed with fire-resisting construction; or

ii. be remote from the stair to the gallery and positioned such that they do not prejudice the escape from the gallery.

see also the pages on Basements,  Stairs and Spiral stairs

Basements

2.13 Because of the risk that a single stairway may be blocked by smoke from a fire in the basement or ground storey, if the basement storey[for the purposes of part B of the Approved Documents] - A storey with a floor which at some point is more than 1200mm below the highest level of ground adjacent to the outside walls. contains any habitable room, the dwellinghouse should be provided with either:

a. an external door or window suitable for egress from the basement (see paragraph 2.8); or

b. a protected stairway leading from the basement to a final exit.

Cavity barriers

2.14  Cavity[for the purposes of part B of the Approved Documents] - A space enclosed by elements of a building (including a suspended ceiling) or contained within an element, but not a room, cupboard, circulation space, protected shaft or space within a fluepipe to conduct gas, typically ventilation air or boiler exhaust. see Flue, chute, duct, pipe or conduit. barriers should be provided above the enclosures to a protected stairway in a dwelling house with a floor more than 4.5m above ground level (see Diagram 6).

see the sections on stair design and spiral stairs.

External escape stairs

2.15  Where an external escape stair is provided, it should meet the following provisions:

a. All doors giving access to the stair should be fire-resisting, except that a fire-resisting door is not required at the head of any stair leading downwards where there is only one exit from the building onto the top landing.

b. Any part of the external envelope of the building within 1800mm of (and 9m vertically below) the flights and landings of an external escape stair should be of fire-resisting construction, except that the 1800mm dimension may be reduced to 1100mm above the top level of the stair if it is not a stair up from a basement to ground level (see Diagram 7).

c. There is protection by fire-resisting construction for any part of the building (including any doors) within 1800mm of the escape route from the stair to a place of safety, unless there is a choice of routes from the foot of the stair that would enable the people escaping to avoid exposure to the effects of the fire in the adjoining building.

d. Any stair more than 6m in vertical extent is protected from the effects of adverse weather conditions. (This should not be taken to imply a full enclosure. Much will depend on the location of the stair and the degree of protection given to the stair by the building itself).

e. Glazing in areas of fire-resisting construction mentioned above should also be fire-resisting (integrity but not insulation) and fixed shut.

Air circulation systems in houses with a floor more than 4.5m above ground level

2.16 Air circulation systems which circulate air within an individual dwelling house with a floor more than 4.5m above ground level should meet the guidance given in paragraph 2.17. Where ventilation ducts pass through compartment walls into another building then the guidance given in Approved Document B Volume 2 should be followed.

2.17 With these types of systems, the following precautions are needed to avoid the possibility of the system allowing smoke or fire to spread into a protected stairway:

a. Transfer grilles should not be fitted in any wall, door, floor or ceiling enclosing a protected stairway.

b. Any duct passing through the enclosure to a protected stairway or entrance hall should be of rigid steel construction and all joints between the ductwork and the enclosure should be fire-stopped.

c. Ventilation ducts supplying or extracting air directly to or from a protected stairway, should not serve other areas as well.

d. Any system of mechanical ventilation which recirculates air and which serves both the stairway and other areas should be designed to shut down on the detection of smoke within the system.

e. A room thermostat for a ducted warm air heating system should be mounted in the living room, at a height between 1370mm and 1830mm, and its maximum setting should not exceed 27°C.

see Disabled access and the part regarding wheelchair lifts

Passenger lifts

2.18 Where a passenger lift is provided in the dwelling house and it serves any floor more than 4.5m above ground level, it should either be located in the enclosure to the protected stairway (see paragraph 2.6) or be contained in a fire- resisting lift shaft.

Work on existing houses

Replacement windows

2.19 Regulation 4(1) requires that all “building work”, as defined by Regulation 3, complies with the applicable requirements of Schedule 1 to the Building Regulations. The definition of building work in Regulation 3(1) includes the provision or extension of a “controlled service or fitting” in or in connection with a building. The definition of controlled service or fitting is given in Regulation 2(1), and includes a replacement window.

Where windows are to be replaced (but not where they are to be repaired only, as repair work to windows does not fall within the definition of building work) the replacement work should comply with the requirements of Parts L and N of Schedule 1. In addition, the building should not have a lesser level of compliance, after the work has been completed, with other applicable Parts of Schedule 1.

For the purposes of Part B1, where a window is located such that, in a new dwellinghouse, an escape window would be necessary and the window is of sufficient size that it could be used for the purposes of escape then:

a. the replacement window opening should be sized to provide at least the same potential for escape as the window it replaces; or

b. where the original window is larger than necessary for the purposes of escape, the window opening could be reduced down to the minimum specified in paragraph 2.8.

Note: Part B3 makes provisions for cavity barriers around window openings in some forms of construction. Where windows are replaced it may be necessary to consider if adequate protection is maintained.

Material alterations

2.20 Paragraph 0.20 sets out the requirements relating to material alterations. What constitutes reasonable provision where undertaking material alterations would depend on the circumstances in the particular case and would need to take account of historic value (see paragraph 0.29). Possible ways of satisfying the requirements include:

a. Smoke alarms

Where new habitable rooms are provided then smoke alarms should be provided in accordance with paragraph 1.8.

b. Loft conversions

Where a new storey is to be added by converting an existing roof space, the provisions for escape need to be considered throughout the full extent of the escape route. For example, a loft conversion to a two-storey house will result in the need to protect the stairway (by providing fire-resisting doors and partitions) where previously no protection may have existed (see paragraph 2.6a).

Note: If it is considered undesirable to replace existing doors (e.g. if they are of historical or architectural merit) it may be possible to retain the doors or upgrade them to an acceptable standard.

Note: Where an ‘open-plan’ arrangement exists at ground level it may be necessary to provide a new partition to enclose the escape route (see Diagram 2).

Alternatively, it may be possible to provide sprinkler protection to the open-plan area, in conjunction with a fire-resisting partition and door (E20), in order to separate the ground floor from the upper storeys. This door should be so arranged to allow the occupants of the loft room to access an escape window at first floor level (in accordance with paragraph 2.8) in the event of a fire in the open-plan area. Cooking facilities should be separated from the open-plan area with fire-resisting construction.

Guidance

Performance

In the Secretary of State’s view the Requirements of B2 will be met if the spread of flame over the internal linings of the building is restricted by making provision for them to have low rates of surface spread of flame and, in some cases, to have a low rate of heat release, so as to limit the contribution that the fabric of the building makes to fire growth. In relation to the European fire tests and classification system, the requirements of B2 will be met if the heat released from the internal linings is restricted by making provision for them to have a resistance to ignition and a rate of fire growth which are reasonable in the circumstances.

The extent to which this is necessary is dependent on the location of the lining.

Introduction

Fire spread and internal linings

see more on Internal Linings, particularly alternatives to plasterboard

B2.i The choice of materials for walls and ceilings can significantly affect the spread of a fire and its rate of growth, even though they are not likely to be the materials first ignited.

It is particularly important in circulation spaces where linings may offer the main means by which fire spreads and where rapid spread is most likely to prevent occupants from escaping.

Several properties of lining materials influence fire spread. These include the ease of ignition and the rate at which the lining material gives off heat when burning. The guidance relating to the European fire tests and classification provides for control of internal fire spread through control of these properties. This document does not give detailed guidance on other properties, such as the generation of smoke and fumes.

Floors and stairs

B2.ii The provisions do not apply to the upper surfaces of floors and stairs because they are not significantly involved in a fire until it is well developed, and thus do not play an important part in fire spread in the early stages of a fire that are most relevant to the safety of occupants.

Other controls on internal surface properties

B2.iii In Section 7 there is guidance on enclosures to above ground drainage system pipes.

Note: External flame spread is dealt with in Sections 8 to 10.

Furniture and fittings

B2.iv Furniture and fittings can have a major effect on fire spread but it is not possible to control them through Building Regulations. They are therefore not dealt with in this Approved Document.

Classification of performance

B2.v Appendix A describes the different classes of performance and the appropriate methods of test (see paragraphs 7 -20).

The national classifications used are based on tests in BS 476 Fire tests on building materials and structures, namely BS 476-6:1989 Method of test for fire propagation for products and BS 476-7:1997 Method of test to determine the classification of the surface spread of flame of products. However, BS 476-4:1970 Non- combustibility test for materials and BS 476- 11:1982 Method for assessing the heat emission from building products are also used as one method of meeting Class 0[for the purposes of of the Approved Documents] - part B1 (Fire Safety) A product performance classification for wall and ceiling linings. The relevant test criteria are set out in Appendix A, paragraph 13 . Other tests are available for classification of thermoplastic materials if they do not have the appropriate rating under BS 476: Part 7; three ratings, referred to as TP(a) rigid and TP(a) flexible and TP(b), are used.

The European classifications are described in BS EN 13501-1:2002 Fire classification of construction products and building elements, Part 1 Classification using data from reaction to fire tests. They are based on a combination of four European test methods, namely:

• BS EN ISO 1182:2002, Reaction to fire tests for building products — Non combustibility test

• BS EN ISO 171 6:2002, Reaction to fire tests for building products – Determination of the gross calorific value

• BS EN 13823:2002, Reaction to fire tests for building products – Building products excluding floorings exposed to the thermal attack by a single burning item

• BS EN ISO 11925-2:2002, Reaction to fire tests for building products, Part 2 Ignitability when subjected to direct impingement of flame.

For some building products, there is currently no generally accepted guidance on the appropriate procedure for testing and classification in accordance with the harmonised European fire tests. Until such a time that the appropriate European test and classification methods for these building products are published classification may only be possible using existing national test methods.

Table A8, in Appendix A, gives typical performance ratings which may be achieved by some generic materials and products.

Section 3: Wall and ceiling linings

Classification of linings

note that this part of the regulation puts strict limits on how much of walls and ceilings can be clad in timber boarding (unless the boarding is treated to a class 1 rating)

3.1 Subject to the variations and specific provisions described in paragraphs 3.2 to 3.16, the surface linings of walls and ceilings should meet the following classifications:

Definition of walls

3.2 For the purpose of the performance of wall linings, a wall includes:

a. the surface of glazing (except glazing in doors); and

b. any part of a ceiling which slopes at an angle of more than 70 deg. to the horizontal.

But a wall does not include:

c. doors and door frames;

d. window frames and frames in which glazing is fitted;

e. architraves, cover moulds, picture rails, skirtings and similar narrow members; or

f. fireplace surrounds, mantle shelves and fitted furniture.

Definition of ceilings

3.3 For the purposes of the performance of ceiling linings, a ceiling includes:

a. the surface of glazing;

b. any part of a wall which slopes at an angle of 700 or less to the horizontal;

c. the underside of a gallery; and

d. the underside of a roof exposed to the room below.

But a ceiling does not include:

e. trap doors and their frames;

f. the frames of windows or rooflights (see Appendix E) and frames in which glazing is fitted; or

g. architraves, cover moulds, picture rails, exposed beams and similar narrow members.

Variations and special provisions

see more on Walls

Walls

3.4 Parts of walls in rooms may be of a poorer performance than specified in paragraph 3.1 (but not poorer than Class 3 (National class) or Class D-s3, d2 (European class) provided the total area of those parts in any one room does not exceed one half of the floor area of the room, subject to a maximum of 20m².

Fire-protecting suspended ceilings

3.5 A suspended ceiling can contribute to the overall fire resistance of a floor/ceiling assembly. Such a ceiling should satisfy paragraph 3.1. It should also meet the provisions of Appendix A, Table A3.

Fire-resisting ceilings

3.6 Cavity barriers are needed in some concealed floor or roof spaces (see Section 6), however, this need can be reduced by the use of a fire-resisting ceiling below the cavity.

see more on Rooflights

Rooflights

3.7 Rooflights should meet the relevant classification in 3.1. However, plastic rooflights with at least a Class 3 rating may be used where 3.1 calls for a higher standard, provided the limitations in Table 2 and in Table 6 are observed.

Note: No guidance is currently possible on the performance requirements in the European fire tests as there is no generally accepted test and classification procedure.

Thermoplastic materials

General

note that a roof light is defined here as “A dome light, lantern light, skylight, ridge light, glazed barrel vault or other element intended to admit daylight through a roof”.

3.8  Thermoplastic materials (see Appendix A, paragraph 17) which cannot meet the performance given in Table 1, can nevertheless be used in windows, roof lights and lighting diffusers in suspended ceilings if they comply with the provisions described in paragraphs 3.10 to 3.14. Flexible thermoplastic material[for the purposes of part B of the Approved Documents] - See Appendix A, paragraph 17. may be used in panels to form a suspended ceiling if it complies with the guidance in paragraph 3.16. The classifications used in paragraphs 3.11 to 3.16, Table 2 and Diagram 9 are explained in Appendix A, paragraph 20.

Note: No guidance is currently possible on the performance requirements in the European fire tests as there is no generally accepted test and classification procedure.

Windows and internal glazing

3.9 External windows to rooms (though not to circulation spaces) may be glazed with thermoplastic materials, if the material can be classified as a TP(a) rigid product.

Internal glazing should meet the provisions in paragraph 3.1.

Notes:

1. A ‘wall’ does not include glazing in a door (see paragraph 3.2).

2. Attention is drawn to the guidance on the safety of glazing in Approved Document N Glazing — safety in relation to impact, opening and cleaning.

Rooflights

3.10 Rooflights to rooms and circulation spaces (with the exception of protected stairways) may be constructed of a thermoplastic material if:

a. the lower surface has a TP(a) (rigid) or TP(b) classification

b. the size and disposition of the rooflights accords with the limits in Table 2 and with the guidance to B4 in Table 7.

see more on Lighting

Lighting diffusers

3.11 The following provisions apply to lighting diffusers which form part of a ceiling. They are not concerned with diffusers of light fittings which are attached to the soffit of, or suspended beneath a ceiling (see Diagram 8).

Lighting diffusers are translucent or open-structured elements that allow light to pass through. They may be part of a luminaire or used below rooflights or other sources of light.

3.12 Thermoplastic lighting diffusers should not be used in fire-protecting or fire-resisting ceilings, unless they have been satisfactorily tested as part of the ceiling system that is to be used to provide the appropriate fire protection.

3.13 Subject to the above paragraphs, ceilings to rooms and circulation spaces (but not protected stairways) may incorporate thermoplastic lighting diffusers if the following provisions are observed:

a. Wall and ceiling surfaces exposed within the space above the suspended ceiling (other than the upper surfaces of the thermoplastic panels) should comply with the general provisions of paragraph 3.1, according to the type of space below the suspended ceiling;

b. If the diffusers are of classification TP(a) (rigid), there are no restrictions on their extent;

c. If the diffusers are of classification TP(b), they should be limited in extent as indicated in Table 2 and Diagram 9.

Suspended or stretched-skin ceilings

3.14 The ceiling of a room may be constructed either as a suspended or stretched-skin membrane from panels of a thermoplastic material of the TP(a) flexible classification, provided that it is not part of a fire-resisting ceiling. Each panel should not exceed 5m² in area and should be supported on all its sides.

this section is guidance on the fire resistance of the main structure. See also the pages on Main Structure.  It also has considerable bearing on the layout of the rooms in a house and the type of structure being used. For instance SIPsStructural Insulated Panels - prefabricated (usually in a factory) timber panels often forming part of an integrated building system and aimed at fast site erection. see more on SIPs houses and timber frame structures need a different approach to fire resistance than traditional masonry construction

Guidance

Performance

In the Secretary of State’s view the Requirements of B3 will be met:

a. if the loadbearing elements of structure of the building are capable of withstanding the effects of fire for an appropriate period without loss of stability;

b. if the building is sub-divided by elements of fire-resisting construction into compartments;

c. if any openings in fire-separating(as applied to the Building Regulations) refers to an element such as a compartment wall, compartment floor, cavity barrier and construction enclosing a protected escape route and/or a place of special fire hazard elements (see Appendix E) are suitably protected in order to maintain the integrity of the element (i.e. the continuity of the fire separation); and

d. if any hidden voids in the construction are sealed and sub-divided to inhibit the unseen spread of fire and products of combustion, in order to reduce the risk of structural failure and the spread of fire, in so far as they pose a threat to the safety of people in and around the building.

The extent to which any of these measures are necessary is dependent on the use of the building and, in some cases, its size, and on the location of the element of construction.

Introduction

B3.i Guidance on loadbearing elements of structure is given in Section 4. Section 5 is concerned with the sub- division of a building into compartments, and Section 6 makes provisions about concealed spaces (or cavities). Section 7 gives information on the protection of openings and on fire-stopping which relates to compartmentation and to fire spread in concealed spaces. Common to all these sections and to other provisions of Part B, is the property of fire resistance.

Fire resistance

B3.ii The fire resistance of an element of construction is a measure of its ability to withstand the effects of fire in one or more ways, as follows:

a. resistance to collapse, i.e. the ability to maintain loadbearing capacity (which applies to load bearing elements only);

b. resistance to fire penetration, i.e. an ability to maintain the integrity of the element; and

c. resistance to the transfer of excessive heat, i.e. an ability to provide insulation from high temperatures.

B3.iii ‘Elements of structure’ is the term applied to the main structural loadbearing elements, such as structural frames, floors and loadbearing walls. Compartment walls are treated as elements of structure although they are not necessarily loadbearing. Roofs, unless they serve the function of a floor, are not treated as elements of structure. External walls, such as curtain walls or other forms of cladding which transmit only self weight and wind loads and do not transmit floor load, are not regarded as loadbearing for the purposes of B3ii(a), although they may need fire resistance to satisfy requirement B4 (see Sections 8 to 9).

Loadbearing elements may or may not have a fire-separating function. Similarly, fire-separating elements may or may not be loadbearing.

Guidance elsewhere in the Approved Document concerning fire resistance

B3.iv There is guidance in Section 2 concerning the use of fire-resisting construction to protect means of escape. There is guidance in Section 9 about fire resistance of external walls to restrict the spread of fire between buildings. Appendix A gives information on methods of test and performance for elements of construction. Appendix B gives information on fire doors. Appendix C gives information on methods of measurement. Appendix D gives information on purpose groupA classification of a building according to the purpose to which it is intended to be put. See Appendix D, Table D1. classification. Appendix E gives definitions.

Section 4: Loadbearing elements of structure

Introduction

see also Main Structure. The fire resistance required for various parts of a house can have an important bearing on other aspects such as cost, insulation, sound proofing etc.

4.1 Premature failure of the structure can be prevented by provisions for loadbearing elements of structure to have a minimum standard of fire resistance, in terms of resistance to collapse or failure of load bearing capacity. The purpose in providing the structure with fire resistance is threefold, namely:

a. to minimise the risk to the occupants, some of whom may be unable to make their own escape if they have become trapped or injured;

b. to reduce the risk to firefighters, who may be engaged in search or rescue operations; and

c. to reduce the danger to people in the vicinity of the building, who might be hurl by falling debris or as a result of the impact of the collapsing structure on other buildings.

Fire resistance standard

4.2 Elements of structure such as structural frames, beams, columns, loadbearing walls (internal and external), floor structures and gallery structures should have at least the fire resistance given in Appendix A, Table Al.

Application of the fire resistance standards for loadbearing elements

this is an important factor in alteration work where, for instance, a new beamSubstantial, usually horizontal structural member. or joist has to not only support the structure above but must also be fire resistant.

4.3 The measures set out in Appendix A include provisions to ensure that where one element of structure supports or gives stability to another element of structure, the supporting element has no less fire resistance than the other element (see notes to Table A2). The measures also provide for elements of structure that are common to more than one building or compartment, to be constructed to the standard of the greater of the relevant provisions. Special provisions about fire resistance of elements of structure in single storey buildings are also given and there are concessions in respect of fire resistance of elements of structure in basements where at least one side of the basement is open at ground level.

Exclusions from the provisions for elements of structure

4.4 The following are excluded from the definition of element of structure for the purposes of these provisions:

a. structure that only supports a roof, unless:

i. the roof performs the function of a floor, such as a roof terrace, or as a means of escape (see Section 2), or

ii. the structure is essential for the stability of an external wall which needs to have fire resistance; and

b. the lowest floor of the building.

Additional guidance

4.5 Guidance in other sections of this Approved Document may also apply if a loadbeanng wall is:

a. a compartment wall[for the purposes of part B of the Approved Documents] - A fire-resisting wall used in the separation of one fire compartment from another. (Constructional provisions are given in Section 5.) (this includes a wall common to two buildings), (see Section 5);

b. a wall between a dwellinghouse and an integral garage, (see Section 5, paragraph 5.4);

c. protecting a means of escape, (see Section 2); or

d. an external wall, (see Sections 8 to 9).

4.6 If a floor is also a compartment floor[for the purposes of part B of the Approved Documents] - A fire-resisting floor used in the separation of one fire compartment from another. (Constructional provisions are given in Section 5.) , see Section 5.

Floors in loft conversions

there are also special provisions for headroom above stairs which serve an attic conversion. see part K , page 7

4.7 In altering an existing two-storey single family dwellinghouse to provide additional storeys, the provisions in this Approved Document are for the floor(s), both old and new, to have the full 30 minute standard of fire resistance shown in Appendix A, Table Al. However, provided that the following conditions are satisfied, namely:

a. only one storey is being added;

b. the new storey contains no more than 2 habitable rooms; and

c. the total area of the new storey does not amount to more than 50m²;

then the existing first floor construction may be accepted if it has at least a modified 30 minute standard of fire resistance, in those places where the floor separates only rooms (and not circulation spaces).

Notes:

1. The ‘modified 30 minute’ standard satisfies the test criteria for the full 30 minutes in respect of loadbearing capacity, but allows reduced performances for integrity and insulation (see Appendix A, Table Al, item 3(a)).

2. A floor which forms part of the enclosure to the circulation space between the loft conversion and the final exit needs a full 30 minute standard.

 A flat is defined as  ‘A separate and self contained premises constructed or adapted for use for residential purposes and forming part of a building from some other part of which it is divided horizontally.’

Conversion to flats

4.8 Where an existing dwellinghouse or other building is converted into flats the guidance in Volume 2 should be followed.

Section 5: Compartmentation

Introduction

5.1 The spread of fire within a building can be restricted by sub-dividing it into compartments separated from one another by walls and/or floors of fire-resisting construction. The object is twofold:

a. to prevent rapid fire spread which could trap occupants of the building; and

b. to reduce the chance of fires becoming large, on the basis that large fires are more dangerous, not only to occupants and fire and rescue service personnel, but also to people in the vicinity of the building.

Compartmentation is complementary to provisions made in Section 2 for the protection of escape routes, and to provisions made in Sections 8 to 10 against the spread of fire between buildings.

Provision of compartmentation

5.2 Compartment walls and compartment floors should be provided in the circumstances described below, with the proviso that the lowest floor in a building does not need to be constructed as a compartment floor. Provisions for the protection of openings in compartment walls and compartment floors are given in paragraph 5.13 and Section 7.

Although the commonest method of building compartment walls between terrace houses or semis is to use a masonry wall, it is also possible to use timber construction sheathed in non combustible material such as plasterboard

5.3 Every wall separating semi-detached houses, or houses in terraces, should be constructed as a compartment wall and the houses should be considered as separate buildings.

5.4 If a domestic garage is attached to (or forms an integral part of) a dwellinghouse, the garage should be separated from the rest of the dwellinghouse, as shown in Diagram 10.

5.5 Where a door is provided between a dwellinghouse and the garage, the floor of the garage should be laid to fall to allow fuel spills to flow away from the door to the outside. Alternatively, the door opening should be positioned at least 100mm above garage floor level.

Construction of compartment walls and compartment floors

General

5.6 Every compartment wall and compartment floor should:

a. form a complete barrier to fire between the compartments they separate; and

b. have the appropriate fire resistance as indicated in Appendix A, Tables Al and A2.

Note: Timber beams, joists, purlins and rafters may be built into or carried through a masonry or concrete compartment wall if the openings for them are kept as small as practicable and then fire-stopped. If trussed rafters bridge the wall, they should be designed so that failure of any part of the truss due to a fire in one compartment will not cause failure of any part of the truss in another compartment.

Compartment walls between buildings

5.7 Compartment walls that are common to two or more buildings should run the full height of the building in a continuous vertical plane. Thus adjoining buildings should only be separated by walls, not floors.

5.8 Compartment walls in a top storey beneath a roof should be continued through the roof space (see definition of compartment in Appendix E).

Junction of compartment wall or compartment floor with other walls

5.9 Where a compartment wall or compartment floor meets another compartment wall, or an external wall, the junction should maintain the fire resistance of the compartmentation. Fire-stopping should meet the provisions of paragraphs 7.12 to 7.14.

5.10 At the junction of a compartment floor with an external wall that has no fire resistance (such as a curtain wall) the external wall should be restrained at floor level to reduce the movement of the wall away from the floor when exposed to fire.

Junction of compartment wall with roof

5.11 A compartment wall should be taken up to meet the underside of the roof covering or deck, with fire-stopping where necessary at the wall! roof junction to maintain the continuity of fire resistance. The compartment wall should also be continued across any eaves.

5.12 If a fire penetrates a roof near a compartment wall there is a risk that it will spread over the roof to the adjoining compartment. To reduce this risk either:

a. the wall should be extended up through the roof for a height of at least 375mm above the top surface of the adjoining roof covering (see Diagram 11a). Where there is a height difference of at least 375mm between two roofs or where the roof coverings on either side of the wall are M, AB or AC this height may be reduced to 200mm; or

b. a zone of the roof 1500mm wide on either side of the wall should have a covering of designation AA, AB or AC. Any combustible boarding used as a substrate to the roof covering, wood wool slabs, or timber tiling battensNarrow strips of wood. Roof battens are narrow strips used to fix slates and tiles. Also used for tile and slate hanging on walls and rain screens that are carried over the compartment wall should be fully bedded in mortar or other suitable material over the width of the wall (see Diagram 11b).

Note: Double-skinned insulated roof sheeting with a thermoplastic core should incorporate a band of material of limited combustibility[for the purposes of part B of the Approved Documents] - A material performance specification that includes non-combustible materials, and for which the relevant test criteria are set out in Appendix A, paragraph 9. at least 300mm wide centred over the wall.

Openings in compartmentation

Openings in compartment walls separating buildings or occupancies

note that the definition of a pipe here “Includes pipe fittings and accessories; and excludes a flue pipe and a pipe used for ventilating purposes (other than a ventilating pipe for an above around drainage system).”

5.13 Any openings in a compartment wall which is common to two or more buildings should be limited to those for:

a. a door which is needed to provide a means of escape in case of fire and which has the same fire resistance as that required for the wall (see Appendix B, Table B1) and is fitted in accordance with the provisions of Appendix B; and

b. the passage of a pipe which meets the provisions in Section 7.

Doors

5.14 Information on fire doors may be found in Appendix B.

Section 6: Concealed spaces (cavities)

Introduction

6.1 Concealed spaces or cavities in the construction of a building provide a ready route for smoke and flame spread e.g. in walls, floors, ceilings and roofs. As any spread is concealed, it presents a greater danger than would a more obvious weakness in the fabric of the building.

Provision of cavity barriers

6.2 Provisions are given below for cavity barriers in specified locations. The provisions necessary to restrict the spread of smoke and flames through cavities are broadly for the purpose of sub-dividing cavities, which could otherwise form a pathway around a fire separating element, and closing the edges of cavities; therefore reducing the potential for unseen fire spread. See also paragraph 2.14.

Note: These should not be confused with fire stopping details, see Sections 5 and 7.

Consideration should also be given to the construction and fixing of cavity barriers provided for these purposes and the extent to which openings in them should be protected. For guidance on these issues, see paragraphs 6.6 to 6.9 respectively.

6.3 Cavity barriers should be provided at the edges of cavities, including around openings (such as window and door openings). Additionally, cavity barriers should be provided at the junction between an external cavity wall and a compartment wall that separates buildings, see Diagram 12; and at the top of such an external cavity wall, except where the cavity wall complies with Diagram 13.

It is important to continue any compartment wall up through a ceiling or roof cavity to maintain the standard of fire resistance — therefore compartment walls should be carried up to the roof, see paragraph 5.11. It is not appropriate to complete a line of compartment walls by fitting cavity barriers above them.

Double-skinned insulated roof sheeting

6.4 Cavity barriers need not be provided between double-skinned corrugated or profiled insulated roof sheeting, if the sheeting is a material of limited combustibility; and both surfaces of the insulating layer have a surface spread of flame of at least Class 0 or 1 (National class) or Class C-s3, d2 or better (European class) (see Appendix A); and make contact with the inner and outer skins of cladding.

Note: When a classification includes “s3, d2”, this means that there is no limit set for smoke production and/or flaming droplets/particles.

Construction and fixings for cavity barriers

6.5 Every cavity barrier[for the purposes of part B of the Approved Documents] - A construction, other than a smoke curtain, provided to close a concealed space[for the purposes of part B of the Approved Documents] - A space enclosed by elements of a building (including a suspended ceiling) or contained within an element, but not a room, cupboard, circulation space, protected shaft or space within a flue, chute, duct, pipe or conduit. against penetration of smoke or flame, or provided to restrict the movement of smoke or flame within such a space should be constructed to provide at least 30 minutes fire resistance and may be formed by any construction provided for another purpose if it meets the provisions for cavity barriers (see Appendix A, Table Al, item 10).

However, cavity barriers in a stud wall or partition, or provided around openings may be formed of:

a. steel at least 0.5mm thick; or

b. timber at least 38mm thick; or

c. polythene-sleeved mineral wool, or mineral wool slab, in either case under compression when installed in the cavity; or

d. calcium silicate, cement-based or gypsum- based boards at least 12mm thick.

Note: Cavity barriers provided around openings may be formed by the window or door frame if the frame is constructed of steel or timber of the minimum thickness in (a) or (b) above as appropriate.

6.6 A cavity barrier should, wherever possible, be tightly fitted to a rigid construction and mechanically fixed in position. Where this is not possible (for example, in the case of a junction with slates, tiles, corrugated sheeting or similar materials) the junction should be fire-stopped. Provisions for fire-stopping are set out in Section 7.

6.7 Cavity barriers should also be fixed so that their performance is unlikely to be made ineffective by:

a. movement of the building due to subsidence, shrinkage or temperature change; and movement of the external envelope due to wind; and

b. collapse in a fire of any services penetrating them; and

c. failure in a fire of their fixings (but see note below); and

d. failure in a fire of any material or construction which they abut. (For example, if a suspended ceiling is continued over the top of a fire- resisting wall or partition, and direct connection is made between the ceiling and the cavity barrier above the line of the wall or partition, premature failure of the cavity barrier can occur when the ceiling collapses. However, this may not arise if the ceiling is designed to provide fire resistance of 30 minutes or more.)

Note: Where cavity barriers are provided in roof spaces, the roof members to which they are fitted are not expected to have any fire resistance (for the purpose of supporting the cavity barrier(s)).

Openings in cavity barriers

6.8 Any openings in a cavity barrier should be limited to those for:

a. doors which have at least 30 minutes fire resistance (see Appendix B, Table 91, item 1(a)) and are fitted in accordance with the provisions of Appendix B;

b. the passage of pipes which meet the provisions in Section 7;

c. the passage of cables or conduits containing one or more cables;

d. openings fitted with a suitably mounted automatic fire damper; and

e. ducts which are fire-resisting or are fitted with a suitably mounted automatic fire damper where they pass through the cavity barrier.

Section 7: Protection of openings and fire-stopping

Introduction

7.1 Sections 7 and 8 make provisions for fire-separating elements and set out the circumstances in which there may be openings in them. This section deals with the protection of openings in such elements.

7.2 If a fire-separating element[for the purposes of part B of the Approved Documents] - A compartment wall, compartment floor, cavity barrier and construction enclosing a protected escape route and/or a place of special fire hazard. is to be effective, then every joint, or imperfection of fit, or opening to allow services to pass through the element, should be adequately protected by sealing or fire-stopping so that the fire resistance of the element is not impaired.

7.3 The measures in this section are intended to delay the passage of fire. They generally have the additional benefit of retarding smoke spread but the test specified in Appendix A for integrity does not directly stipulate criteria for the passage of smoke.

7.4 Consideration should also be given to the effect of services that may be built into the construction that could adversely affect its fire resistance. For instance, where downlighters, loudspeakers and other electrical accessories are installed, additional protection may be required to maintain the integrity of a wall or floor.

7.5 Detailed guidance on door openings and fire doors is given in Appendix B.

Openings for pipes

7.6 Pipes which pass through fire-separating elements (unless the pipe is in a protected shaft), should meet the appropriate provisions in alternatives A, B or C below.

Alternative A: Proprietary seals (any pipe diameter)

7.7 Provide a proprietary sealing system which has been shown by test to maintain the fire resistance of the wall, floor or cavity barrier.

Alternative B: Pipes with a restricted diameter

7.8 Where a proprietary sealing system is not used, fire-stopping may be used around the pipe, keeping the opening as small as possible. The nominal internal diameter of the pipe should not be more than the relevant dimension given in Table 3.

Alternative C: sleeving

7.9 A pipe of lead, aluminium, aluminium alloy, fibre-cement or uPVC, with a maximum nominal internal diameter of 160mm, may be used with a sleeving of non-combustible pipe as shown in Diagram 14. The specification for non-combustible and uPVC pipes is given in the notes to Table 3.

Bear in mind that services which pass through a separating element may reduce sound insulation as well

so 7.10 may affect ventilation ducts in PassivhausSee more on the Passivhaus standard. The PassivHaus Institute has pioneered a standard for low energy buildings. It includes very low energy usage and ways of achieving this. The word is derived from the idea of buildings which are fundamentally low energy and passive solar heated rather than using extra gadgets to heat them. See Passivhaus for the UK branch of the organisation. construction

Ventilation ducts, fluespipe to conduct gas, typically ventilation air or boiler exhaust. see more on Flues etc.

7.10 Air circulation systems which circulate air within an individual dwellinghouse with a floor more than 4.5m above ground level should meet the guidance given in paragraph 2.16. Where ventilation ducts pass through compartment walls into another building then the guidance given in Approved Document B Volume 2 should be followed.

7.11 If a flue or duct containing flues or appliance ventilation duct[for the purposes of part B of the Approved Documents] - A duct provided to convey combustion air to a gas appliance.(s), passes through a compartment wall or compartment floor, or is built into a compartment wall, each wall of the flue or duct should have a fire resistance of at least half that of the wall or floor in order to prevent the by-passing of the compartmentation (see Diagram 16).

Fire-stopping

7.12 In addition to any other provisions in this document for fire-stopping:

a. joints between fire-separating elements should be fire-stopped; and

b. all openings for pipes, ducts, conduits or cables to pass through any part of a fire-separating element should be:

i. kept as few in number as possible; and

ii. kept as small as practicable; and

iii. fire-stopped (which in the case of a pipe or duct should allow thermal movement).

7.13 To prevent displacement, materials used for fire-stopping should be reinforced with (or supported by) materials of limited combustibility in the following circumstances:

a. in all cases where the unsupported span is greater than 100mm; and

b. in any other case where non-rigid materials are used (unless they have been shown to be satisfactory by test).

7.14 Proprietary fire-stopping and sealing systems, (including those designed for service penetrations) which have been shown by test to maintain the fire resistance of the wall or other element, are available and may be used.

Other fire-stopping materials include:

• cement mortar
• gypsum-based plaster;
• cement-based gypsum-based vermiculite? perlite mixes;
• glass fibre, crushed rock, blast furnace slag or ceramic-based products (with or without resin binders); and
• intumescent mastics.

These may be used in situations appropriate to the particular material. Not all of them will be suitable in every situation.

Guidance on the process of design, installation and maintenance of passive fire protection is available in Ensuring Best Practice for Passive Fire Protection in Buildings (ISBN: 1 87040 919 1) produced by the Association for Specialist Fire Protection (ASFP).

Further information on the generic types of systems available, information about their suitability for different applications and guidance on test methods is given in the ASFP Red Book:

Fire Stopping and Penetration Seals for the Construction Industry — the ‘Red Book’ published by the Association for Specialist Fire Protection and freely available from the ASFP website at www.asfp.org.uk.

This section is about reducing the risk of fire attacking the house from the outside e.g. from a neighbouring building which is on fire

Guidance

Performance

In the Secretary of State’s view the Requirements of B4 will be met:

a. if the external walls are constructed so that the risk of ignition from an external source, and the spread of fire over their surfaces, is restricted by making provision for them to have low rates of heat release;

b. if the amount of unprotected area[for the purposes of part B of the Approved Documents] - In relation to a side or external wall of a building means: a. window, door or other opening; and Note: Windows that are not openable and are designed and glazed to provide the necessary level of fire resistance need not be regarded as an unprotected area. b. any part of the external wall which has less than the relevant fire resistance set out in Section 8. c. any part of the external wall which has combustible material more than 1 mm thick attached or applied to its external face, whether for cladding or any other purpose. Combustible material in this context is any material which does not have a Class 0 rating.) in the side of the building is restricted so as to limit the amount of thermal radiation that can pass through the wall, taking the distance between the wall and the boundary[for the purposes of part B of the Approved Documents] - The boundary of the land belonging to the building, or where the land abuts a road, railway, canal or river, the centre line of that road, railway, canal or river (See Diagram 17.) into account; and

c. if the roof is constructed so that the risk of spread of flame and/or fire penetration from an external fire source is restricted.

In each case so as to limit the risk of a fire spreading from the building to a building beyond the boundary, or vice versa.

The extent to which this is necessary is dependent on the use of the building, its distance from the boundary and, in some cases, its height.

Introduction

External walls

B4.i The construction of external walls and the separation between buildings to prevent external fire spread are closely related.

The chances of fire spreading across an open space between buildings, and the consequences if it does, depend on:

a. the size and intensity of the fire in the building concerned;

b. the distance between the buildings;

c. the fire protection given by their facing sides; and

d. the risk presented to people in the other building(s).

B4.ii Provisions are made in Section 8 for the fire resistance of external walls and to limit the susceptibility of the external surface of walls to ignition and to fire spread.

B4.iii Provisions are made in Section 9 to limit the extent of openings and other unprotected areas[for the purposes of part B of the Approved Documents] - In relation to a side or external wall of a building means: a. window, door or other opening; and Note: Windows that are not openable and are designed and glazed to provide the necessary level of fire resistance need not be regarded as an unprotected area. b. any part of the external wall which has less than the relevant fire resistance set out in Section 8. c. any part of the external wall which has combustible material more than 1 mm thick attached or applied to its external face, whether for cladding or any other purpose. Combustible material in this context is any material which does not have a Class 0 rating.) in external walls in order to reduce the risk of fire spread by radiation.

Roofs

B4.iv Provisions are made in Section 10 for reducing the risk of fire spread between roofs and over the surfaces of roofs.

Section 8: Construction of external walls

Introduction

8.1 Provisions are made in this section for the external walls of the building to have sufficient fire resistance to prevent fire spread across the relevant boundary[for the purposes of part B of the Approved Documents] - The boundary which the side of the building faces, (and/or coincides with) and which is parallel, or at an angle of not more than 800, to the side of the building (see Section 9 Diagram 17). A notional boundary[for the purposes of part B of the Approved Documents] - A boundary presumed to exist between buildings on the same site (see Section 9, Diagram 18). can be a relevant boundary. The provisions are closely linked with those for space separation in Section 9 which sets out limits on the amount of unprotected area of wall. As the limits depend on the distance of the wall from the relevant boundary, it is possible for some or all of the walls to have no fire resistance, except for any parts which are loadbearing (see paragraph B3.iii).

External walls are elements of structure and the relevant period of fire resistance (specified in Appendix A) depends on the use, height and size of the building concerned. If the wall is 1000mm or more from the relevant boundary, a reduced standard of fire resistance is accepted in most cases and the wall only needs fire resistance from the inside.

8.2 Provisions are also made to restrict the combustibility of external walls of buildings that are less than 1000mm from the relevant boundary. This is in order to reduce the surface’s susceptibility to ignition from an external source. In the guidance to Requirement 93, provisions are made in Section 4 for internal and external loadbearing walls to maintain their loadbearing function in the event of fire.

Fire resistance standard

8.3 The external walls of the building should have the appropriate fire resistance given in Appendix A, Table A1, unless they form an unprotected area under the provisions of Section 9.

External surfaces

8.4 The external surfaces of walls within 1000mm of the relevant boundary should meet Class 0 (National Class) or Class B-s3,d2 or better (European class). The total amount of combustible material on walls more than 1000mm from the relevant boundary may be limited in practice by the provisions for space separation in Section 9 (see paragraphs 9.7 to 9.17.).

Section 9: Space separation

Introduction

9.1 The provisions in this Section are based on a number of assumptions and, whilst some of these may differ from the circumstances of a particular case, together they enable a reasonable standard of space separation to be specified. The provisions limit the extent of unprotected areas in the sides of a building (such as openings and areas with a combustible surface) which will not give adequate protection against the external spread of fire from one building to another.

A roof is not subject to the provisions in this Section unless it is pitched at an angle greater than 70° to the horizontal (see definition for ‘external wall’ in Appendix E). Similarly, vertical parts of a pitched roof such as dormer windows (which taken in isolation[for the purposes of part C of the Approved Documents] - The absence of rigid connections between two or more parts of a structure. might be regarded as a wall), would not need to meet the following provisions unless the slope of the roof exceeds 700. It is a matter of judgement whether a continuous run of dormer windows occupying most of a steeply pitched roof should be treated as a wall rather than a roof.

9.2 The assumptions are:

a. that the size of a fire will depend on the compartmentation of the building, so that a fire may involve a complete compartment, but will not spread to other compartments;

b. that the intensity of the fire is related to the use of the building (i.e. purpose group), but that it can be moderated by a sprinkler system;

c. that Residential (1 and 2) and Assembly and Recreation (5) Purpose Groups represent a greater life risk than other uses;

d. that there is a building on the far side of the boundary that has a similar elevation to the one in question and that it is at the same distance from the common boundary; and

e. that the amount of radiation that passes through any part of the external wall that has fire resistance may be discounted.

9.3 Where a reduced separation distance is desired (or an increased amount of unprotected area) it may be advantageous to introduce additional compartment walls and/or floors.

Depending on neighbouring property, the exact positioning of a house on its plot can significantly affect the design of walls, windows, doors and roofs.  In some situations the limitation on unprotected area may tie in well with smaller windows on the north side of a house for heat insulation purposes

Boundaries

9.4 The use of the distance to a boundary, rather than to another building, in measuring the separation distance, makes it possible to calculate the allowable proportion of unprotected areas, regardless of whether there is a building on an adjoining site and regardless of the site of that building and the extent of any unprotected areas that it might have.

A wall is treated as facing a boundary if it makes an angle with it of 80° or less (see Diagram 17).

Usually only the distance to the actual boundary of the site needs to be considered. But, in some circumstances, when the site boundary adjoins a space where further development is unlikely, such as a road, then part of the adjoining space may be included as falling within the relevant boundary for the purposes of this section. The meaning of the term boundary is explained in Diagram 17.

Relevant boundaries

9.5 The boundary which a wall faces, whether it is the actual boundary of the site or a notional boundary, is called the relevant boundary (see Diagrams 17 and 18).

Notional boundaries

9.6 The distances to other buildings on the same site also need to be considered. This is done by assuming that there is a boundary between those buildings. This assumed boundary is called a notional boundary. The appropriate rules are given in Diagram 18.

Unprotected areas

Unprotected areas and fire resistance

9.7 Any part of an external wall which has less fire resistance than the appropriate amount given in Appendix A, Table A2, is considered to be an unprotected area.

Status of combustible surface materials as unprotected area

9.8 If an external wall has the appropriate fire resistance, but has combustible material more than 1 mm thick as its external surface, then that wall is counted as an unprotected area amounting to half the actual area of the combustible material, see Diagram 19. (For the purposes of this provision, a material with a Class 0 rating (National class) or Class B-s3, d2 rating (European class) (see Appendix A, paragraphs 7 and 13) need not be counted as unprotected area.)

Note: When a classification includes ‘s3, d2’, this means that there is no limit set for smoke production and/or flaming droplets/particles.

Small unprotected areas

9.9 Small unprotected areas in an otherwise protected area of wall are considered to pose a negligible risk of fire spread and may be disregarded. Diagram 20 shows the constraints that apply to the placing of such areas in relation to each other and to lines of compartmentation inside the building. These constraints vary according to the size of each unprotected area.

Canopies

9.10 Some canopy structures would be exempt from the application of the Building Regulations by falling within Class 6 or Class 7 of Schedule 2 to the Regulations (Exempt Buildings and Work). Many others may not meet the exemption criteria and, in such cases, the provisions in this section about limits of unprotected areas could be onerous.

In the case of a canopy attached to the side of a building, provided that the edges of the canopy are at least 2m from the relevant boundary, separation distance may be determined from the wall rather than the edge of the canopy (see Diagram 21).

External walls within 1000mm of the relevant boundary

9.11 A wall situated within 1000mm from any point on the relevant boundary, including a wall coincident with the boundary, will meet the provisions for space separation if:

a. the only unprotected areas are those shown in Diagram 20; and

b. the rest of the wall is fire-resisting from both sides.

External walls 1000mm or more from the relevant boundary

9.12  A wall situated at least 1000mm from any point on the relevant boundary will meet the provisions for space separation if:

a. the extent of unprotected area does not exceed that given by one of the methods referred to in paragraph 9.13; and

b. the rest of the wall (if any) is fire-resisting.

Methods for calculating acceptable unprotected area

9.13  Two simple methods are given in this Approved Document for calculating the acceptable amount of unprotected area in an external wall that is at least 1000mm from any point on the relevant boundary. (For walls within 1000mm of the boundary see paragraph 9.11 above.)

Method 1 may be used for small residential buildings and is set out in paragraph 9.16.

Method 2 may be used for most buildings or compartments for which Method 1 is not appropriate, and is set out in paragraph 9.17.

There are other more precise methods, described in a BREBuilding Research Establishment. report External fire spread: Building separation and boundary distances (BR 187, BRE 1991), which may be used instead of Methods 1 and 2. The ‘Enclosing Rectangle’ and ‘Aggregate Notional Area’ methods are included in the BRE report.

Basis for calculating acceptable unprotected area

9.14  The basis of Methods 1 and 2 was originally set out in Fire Research Technical Paper No 5, 1963. This has been reprinted as part of the BRE report referred to in paragraph 9.13. The aim is to ensure that the building is separated from the boundary by at least half the distance at which the total thermal radiation intensity received from all unprotected areas in the wall would be 12.6 kwkilowatt - a measure of how fast energy is flowing. e.g. electricity might flow through an electric kettle at the rate of 2 kW/m² (in still air), assuming the radiation intensity at each unprotected area is 84 kw/m².

Wales has decided to make sprinkler systems mandatory in new houses. The Copper Development Association publish a promotional PDF outlining what is involved with sprinkler systems

Sprinkler systems

9.15 If a building is fitted throughout with a sprinkler system, it is reasonable to assume that the intensity and extent of a fire will be reduced. The sprinkler system should meet the relevant recommendations of BS 9251 Sprinkler systems for residential and domestic occupancies. Code of practice. In these circumstances the boundary distance may be half that for an otherwise similar, but unsprinklered, building, subject to there being a minimum distance of 1000mm. Alternatively, the amount of unprotected area may be doubled if the boundary distance is maintained.

Note: The presence of sprinklers may be taken into account in a similar way when using the BRE report referred to in paragraph 9.14.

Method 1

9.16 This method applies only to a building, which is 1000mm or more from any point on the relevant boundary and meets the following rules for determining the maximum unprotected area, which should be read with Diagram 22:

a. The building should not exceed 3 storeys in height (basements are not counted) or be more than 24m in length; and

b. Each side of the building will meet the provisions for space separation if:

i. the distance of the side of the building from the relevant boundary; and

ii the extent of the unprotected area, are within the limits given in Diagram 22; and

Note: In calculating the maximum unprotected area, any areas falling within the limits shown in Diagram 20, and referred to in paragraph 9.9, can be disregarded.

c. Any parts of the side of the building in excess of the maximum unprotected area should be fire- resisting.

Method 2

9.17 This method applies to a dwellinghouse which is more than 1000mm from any point on the relevant boundary. The following rules for determining the maximum unprotected area should be read with Table 4.

a. The building or compartment should not exceed 10m in height.

Note: For any building or compartment more than 10m in height, the methods set out in the BRE report External fire spread: Building separation and boundary distances can be applied.

b. Each side of the building will meet the provisions for space separation if either

i. the distance of the side of the building from the relevant boundary; or

ii. the extent of unprotected area, are within the appropriate limits given in Table 4.

Note: In calculating the maximum unprotected area, any areas shown in Diagram 20, and

referred to in paragraph 9.9, can be disregarded.

c. Any parts of the side of the building in excess of the maximum unprotected area should be fire- resisting.

Section 10: Roof coverings

Introduction

10.1 The provisions in this section limit the use, near a boundary, of roof coverings which will not give adequate protection against the spread of fire over them. The term roof covering is used to describe constructions which may consist of one or more layers of material, but does not refer to the roof structure as a whole. The provisions in this Section are principally concerned with the performance of roofs when exposed to fire from the outside.

10.2 The circumstances when a roof is subject to the provisions in Section 9 for space separation are explained in paragraph 9.1.

Other controls on roofs

10.3 There are provisions concerning the fire properties of roofs in other Sections of this document. In the guidance to Bi (paragraph 2.10) there are provisions for roofs that are part of a means of escape. In the guidance to 92 there are provisions for the internal surfaces of rooflights as part of the internal lining of a room or circulation space. In the guidance to B3 there are provisions in Section 4 for roofs which are used as a floor and in Section 6 for roofs that pass over the top of a compartment wall.

Classification of performance

10.4 The performance of roof coverings is designated by reference to the test methods specified in BS 476-3:2004 Fire tests on building materials and structures. Classification and method of test for external fire exposure to roofs or determined in accordance with BS EN 13501-5:2005 Fire classification of construction products and building elements. Classification using data from external fire exposure to roof tests, as described in Appendix A. The notional performance of some common roof coverings is given in Table A5 of Appendix A.

Rooflights are controlled on a similar basis, and plastic rooflights described in paragraphs 1 0.6 and 10.7 may also be used.

Separation distances

10.5 The separation distance is the minimum distance from the roof (or part of the roof) to the relevant boundary, which may be a notional boundary.

Table 5 sets out separation distances according to the type of roof covering and the size and use of the building. There are no restrictions on the use of roof coverings designated AA, AB or AC (National class) or BR(t4) (European class) classification. In addition, roof covering products (and/or materials) as defined in Commission Decision 2000/553/EC of 6 September 2000 implementing Council Directive 89/106/EEC as regards the external fire performance of roof coverings can be considered to fulfill all of the requirements for performance characteristic ‘external fire performance’ without the need for testing provided that any national provisions on the design and execution of works are fulfilled.

Note: The boundary formed by the wall separating a pair of semi-detached houses may be disregarded for the purposes of this Section (but see Section 5, Diagram 11(b), which deals with roofs passing over the top of a compartment wall).

Plastic rooflights

10.6 Table 6 sets out the limitations on the use of plastic rooflights which have at least a Class 3 (National class) or Class D-s3, d2 (European class) lower surface, and Table 7 sets out the limitations on the use of thermoplastic materials with a TP(a) rigid or TP(b) classification (see also Diagram 23). The method of classifying thermoplastic materials is given in Appendix A.

10.7 When used in rooflights, a rigid thermoplastic sheet product made from polycarbonate or from unplasticised PVC, which achieves a Class 1 (National class) rating for surface spread of flame when tested to BS 476-7:1997 (or 1987 or 1971), or Class C- s3,d2 (European class) can be regarded as having an AA (National class) designation or BROOF (t4) (European class) classification, other than for the purposes of Diagram 11.

Unwired glass in rooflights

10.8 When used in rooflights, unwired glass at least 4mm thick can be regarded as having an AA designation (National class) or BROOF(t4) (European class) classification.

Thatch and wood shingles

10.9 Thatch and wood shingles should be regarded as having an AD/BD/CD designation or EROOF(t4) (European class) classification in Table 5 if performance under BS 476-3:2004 (or 1958) or BS EN 11 87:xxxx cannot be established.

Note: Consideration can be given to thatched roofs being closer to the boundary than shown in Table 5 if, for example, the following precautions (based on Thatched buildings. New properties and extensions [the ‘Dorset Model’]) are incorporated in the design:

a. the rafters are overdrawn with construction having not less than 30 minutes fire resistance;

b. the guidance given in Approved Document J Combustion appliances and fuel storage is followed; and

c. the smoke alarm installation (see Section 1) extends to the roof space.

This section is about firefighting and access for firefighting vehicles

Guidance

Performance

In the Secretary of State’s view the Requirements of B5 will be met:

a. if there is sufficient means of external access to enable fire appliances to be brought near to the building for effective use;

b. if there is sufficient means of access into, and within, the building for firefighting personnel to effect search and rescue and fight fire;

c. if the building is provided with sufficient internal fire mains and other facilities to assist firefighters in their tasks; and

d. if the building is provided with adequate means for venting heat and smoke from a fire in a basement.

These access arrangements and facilities are only required in the interests of the health and safety of people in and around the building. The extent to which they are required will depend on the use and size of the building in so far as it affects the health and safety of those people.

Introduction

B5.i The main factor determining the facilities needed to assist the fire and rescue service is the size of the building. Generally speaking firefighting is carried out within the building.

For dwelling houses, it is usually only necessary to ensure that the building is sufficiently close to a point accessible to fire and rescue service vehicles (see paragraph 11.2). For very large houses additional measures may be necessary. The guidance given in Approved Document B Volume 2 (Buildings other than dwellinghouses) may be applicable.

If it is proposed to deviate from the general guidance in Section 11 then it would be advisable to seek advice from the Fire and Rescue Service at the earliest opportunity.

Section 11: Vehicle access

Introduction

11.1 For the purposes of this Approved Document, vehicle access to the exterior of a building is needed to enable high reach appliances, such as turntable ladders and hydraulic platforms, to be used and to enable pumping appliances to supply water and equipment for firefighting, search and rescue activities.

Vehicle access routes and hard-standings should meet the criteria described in paragraph 11.4 where they are to be used by fire and rescue service vehicles.

Note: Requirements cannot be made under the Building Regulations for work to be done outside the site of the works shown on the deposited plans, building notice or initial notice. In this connection it may not always be reasonable to upgrade an existing route across a site to a small building such as a single dwellinghouse. The options in such a case, from doing no work to upgrading certain features of the route, e.g. a sharp bend, should be considered by the Building Control Body in consultation with the fire and rescue service.

11.2 There should be vehicle access for a pump appliance to within 45m of all points within the dwellinghouse.

11.3 Every elevation to which vehicle access is provided in accordance with paragraph 11.2 should have a suitable door(s), not less than 750mm wide, giving access to the interior of the building.

Design of access routes and hard-standings

11.4 A vehicle access route may be a road or other route which, including any inspection covers and the like, meets the standards in Table 8 and paragraph 11.5.

11.5 Turning facilities should be provided in any dead end[for the purposes of part B of the Approved Documents] - Area from which escape is possible in one direction only. access route that is more than 20m long (see Diagram 24). This can be by a hammerhead or turning circle, designed on the basis of Table 8.

If it should be necessary to provide access then it may be appropriate to use recycled porous polythene paving systems with grass or recycled gravel infill provided they achieve the necessary loadings. This would be in line with SUDSSustainable urban drainage systems. Various ways of holding back rain water and allowing it to percolate into the ground instead of taking it to a drain and sewer. This helps prevent flash flooding. See Surface rainwater and SUDS principles.

Appendix A: Performance of materials, products and structures

Introduction

1. Much of the guidance in this document is given in terms of performance in relation to British or European Standards for products or methods of test or design or in terms of European Technical Approvals. In such cases the material, product or structure should:

a. be in accordance with a specification or design which has been shown by test to be capable of meeting that performance; or

Note: For this purpose, laboratories accredited by the United Kingdom Accreditation Service (UKASUnited Kingdom Accreditation Service) for conducting the relevant tests would be expected to have the necessary expertise.

b. have been assessed from test evidence against appropriate standards, or by using relevant design guides, as meeting that performance; or

Note: For this purpose, laboratories accredited by UKAS for conducting the relevant tests and suitably qualified fire safety engineers might be expected to have the necessary expertise.

For materials/products where European standards or approvals are not yet available and for a transition period after they become available, British standards may continue to be used. Any body notified to the UK Government by the Government of another Member State of the European Union as capable of assessing such materials/products against the relevant British Standards, may also be expected to have the necessary expertise. Where European materials! products standards or approvals are available, any body notified to the European Commission as competent to assess such materials or products against the relevant European standards or technical approval can be considered to have the appropriate expertise.

c. where tables of notional performance are included in this document, conform with an appropriate specification given in these tables; or

d. in the case of fire-resisting elements:

i. conform with an appropriate specification given in Part II of the Building Research Establishments’ Report Guidelines for the construction of fire-resisting structural elements (BR 128, BRE 1988); or

ii. be designed in accordance with a relevant British Standard or Eurocode.

Note 1: Different forms of construction can present different problems and opportunities for the provision of structural fire protection. Further information on some specific forms of construction can be found in:

• Timber — BRE 454 Multi -storey timber frame buildings — a design guide 2003 ISBN: 1 86081 605 3

• Steel — SCI P197 Designing for structural fire safety: A handbook for architects and engineers 1999 ISBN: 1 85942 074 5

Note 2: Any test evidence used to substantiate the fire resistance rating of a construction should be carefully checked to ensure that it demonstrates compliance that is adequate and applicable to the intended use. Small differences in detail (such as fixing method, joints, dimensions and the introduction of insulation materials etc.) may significantly affect the rating.

2. Building Regulations deal with fire safety in buildings as a whole. Thus they are aimed at limiting fire hazard.

The aim of standard fire tests is to measure or assess the response of a material, product, structure or system to one or more aspects of fire behaviour. Standard fire tests cannot normally measure fire hazard. They form only one of a number of factors that need to be taken into account. Other factors are set out in this publication.

Fire resistance

3. Factors having a bearing on fire resistance, that are considered in this document, are:

a. fire severity;

b. building height; and

c. building occupancy.

4. The standards of fire resistance given are based on assumptions about the severity of fires and the consequences should an element fail. Fire severity is estimated in very broad terms from the use of the building (its purpose group), on the assumption that the building contents (which constitute the fire load) are similar for buildings in the same use.

A number of factors affect the standard of fire resistance specified. These are:

a. the amount of combustible material per unit of floor area in various types of building (the fire load density);

b. the height of the top floor above ground, which affects the ease of escape and of firefighting operations, and the consequences should large scale collapse occur;

c. occupancy type[for the purposes of part B of the Approved Documents] - A purpose group identified in Appendix D., which reflects the ease with which the building can be evacuated quickly;

d. whether there are basements, because the lack of an external wall through which to vent heat and smoke may increase heat build-up and thus affect the duration of a fire, as well as complicating firefighting; and

e. whether the building is of single storey construction (where escape is direct and structural failure is unlikely to precede evacuation).

Because the use of buildings may change, a precise estimate of fire severity based on the fire load due to a particular use may be misleading. Therefore, if a fire engineering approach of this kind is adopted, the likelihood that the fire load may change in the future needs to be considered.

5. Performance in terms of the fire resistance to be met by elements of structure, doors and other forms of construction is determined by reference to either:

a. (National tests) BS 476 Fire tests on building materials and structures, Parts 20-24:1987, i.e. Part 20 Method for determination of the fire resistance of elements of construction (gesi era! principles), Part 21 Methods for determination of the fire resistance of loadbearing elements of construction, Part 22 Methods for determination of the fire resistance of non-Ioadbearing elements of construction, Part 23 Methods for determination of the contribution of components to the fire resistance of a structure, and Part 24 Method for determination of the fire resistance of ventilation ducts (or to BS 476-8:1972 in respect of items tested or assessed prior to 1 January 1988); or

b. (European tests) Commission Decision 2000/367/EC of 3 May 2000 implementing Council Directive 89/106/EEC as regards the classification of the resistance to fire performance of construction products, construction works and parts thereof.

Note: The latest version of any standard may be used provided that it continues to address the relevant requirements of the Regulations.

All products are classified in accordance with BS EN 13501-2:2007 Fire classification of construction products and building elements. Classification using data from fire resistance tests, excluding ventilation services (excluding products for use in ventilation systems).

BS EN 13501-3:2005 Fire classification of construction products and building elements. Classification using data from fire resistance tests on products and elements used in building service installations: fire resisting ducts and fire dampers (other than smoke control systems).

BS EN 13501 -4:2007, Fire classification of construction products and building elements, Part 4 — Classification using data from fire resistance tests on smoke control systems.

The relevant European test methods under BS EN 1364, 1365, 1366 and 1634 are listed in Appendix F.

Table A1 gives the specific requirements for each element in terms of one or more of the following performance criteria:

a. resistance to collapse (loadbearing capacity), which applies to loadbearing elements only, denoted R in the European classification of the resistance to fire performance;

b. resistance to fire penetration (integrity), denoted E in the European classification of the resistance to fire performance; and

c. resistance to the transfer of excessive heat (insulation), denoted I in the European classification of the resistance to fire performance.

Table A2 sets out the minimum periods of fire resistance for elements of structure.

Table A3 sets out criteria appropriate to the suspended ceilings that can be accepted as contributing to the fire resistance of a floor.

Table A4 sets out limitations on the use of uninsulated fire-resisting glazed elements. These limitations do not apply to the use of insulated fire-resisting glazed elements.

Information on tested elements is frequently given in literature available from manufacturers and trade associations.

Information on tests on fire-resisting elements is also given in such publications as:

Association for Specialist Fire Protection Yellow Book — Fire protection for structural steel in buildings, 4th edition. See Appendix F.

Roofs

6. Performance in terms of the resistance of roofs to external fire exposure is determined by reference to either:

a. (National tests) BS 476-3:2004 External fire exposure roof tests; or

b. (European tests) Commission Decision 2005/823/EC amending Decision 2001 /671/ EC Establishing a classification system for the external fire performance of roofs and roof coverings.

Constructions are classified within the National system by two letters in the range A-D, with an M designation being the best. The first letter indicates the time to penetration; the second letter a measure of the spread of flame.

Constructions are classified within the European system as BROOF(t4), CROOF(t4), DROOF(t4), EROOF(t4), FROOF(t4), with BROOF(t4) being the highest performance and FROOF(t4) being the lowest) in accordance with BS EN 13501-5:2005 Fire classification of construction products and building elements — Classification using data from external fire exposure to roof tests.

BS EN 13501-5 refers to four separate tests. The suffix (t4) used above indicates that Test 4 is to be used for the purposes of this Approved Document.

Some roof covering products (and/or materials) can be considered to fulfil all of the requirements for the performance characteristic “external fire performance” without the need for testing, subject to any national provisions on the design and execution of works being fulfilled. These roof covering products are listed in Commission Decision 2000/553/EC of 6th September 2000 implementing Council Directive 89/1 06/EEC as regards the external fire performance of roof coverings.

In some circumstances roofs, or parts of roofs, may need to be fire-resisting, for example if used as an escape route or if the roof performs the function of a floor. Such circumstances are covered in Sections 2, 4 and 6.

Table A5 gives notional designations of some generic roof coverings.

Reaction to fire

7. Performance in terms of reaction to fire to be met by construction products is determined by Commission Decision 200/147/EC of 8 February 2000 implementing Council Directive 89/1 06/EEC as regards the classification of the reaction to fire performance of construction products.

Note: The designation of xxxx is used for the year reference for standards that are not yet published. The latest version of any standard may be used provided that it continues to address the relevant requirements of the Regulations.

All products, excluding floorings, are classified as †A1, A2, B, C, D, E or F (with class A1 being the highest performance and F being the lowest) in accordance with BS EN 13501-1:2002 Fire classification of construction products and building elements, Part 1 — Classification using data from reaction to fire tests.

† The classes of reaction to fire performance of A2, B, C, D and E are accompanied by additional classifications related to the production of smoke s1, s2, s3) and/or flaming droplets/particles (d0,d1,d2).

The relevant European test methods are specified as follows:

• BS EN ISO 1182:2002 Reaction to fire tests for building products – Non-combustibility test

• BS EN ISO 1716:2002 Reaction to fire tests for building products — Determination of the gross calorific value

• BS EN 13823:2002 Reaction to fire tests for building products — Building products excluding floorings exposed to the thermal attack by a single burning item

• BS EN ISO 11925-2:2002 Reaction to fire tests for building products, Part 2— Ignitability when subjec ted to direct impingement of a flame.

• BS EN 13238:2001 Reaction to fire tests for building products — conditioning procedures and general rules for selection of substrates.

Non-combustible materials

8. Non-combustible materials are defined in Table A6 either as listed products, or in terms of performance:

a. (National classes) when tested to BS 476- 4:1970 Fire tests on building materials and structures — Non-combustibility test for materials or BS 476-11:1982 Fire tests on building materials and structures — Method for assessing the heat emission from building materials.

b. (European classes) when classified as class Al in accordance with BS EN 13501-1:2002 Fire classification of construction products and building elements. Classification using data from reaction to fire tests when tested to BS EN ISO 1182:2002 Reaction to fire tests for building products – Non-combustibility test and BS EN ISO 1716:2002 Reaction to fire tests for building products — Determination of the gross calorific value.

Table A6 identifies non-combustible products and materials, and lists circumstances where their use is necessary.

Materials of limited combustibility

9. Materials of limited combustibility are defined in Table A7:

a. (National classes) by reference to the method specified in BS 476-11:1982;

b. (European classes) in terms of performance when classified as class A2-s3, d2 in accordance with BS EN 13501-1:2002 Fire classification of construction products and building elements. Classification using data from reaction to fire tests when tested to BS EN ISO 1182:2002 Reaction to fire tests for building products Non-combustibility test or BS EN ISO 1716:2002 Reaction to fire tests for building products — Determination of the gross calorific value and BS EN 13823:2002 Reaction to fire tests for building products — Building products excluding floorings exposed to the thermal attack by a single burning item.

Table A7 also includes composite products (such as plasterboard) which are considered acceptable, and where these are exposed as linings they should also meet any appropriate flame spread rating.

Internal linings

10. Flame spread over wall or ceiling surfaces is controlled by providing for the lining materials or products to meet given performance levels in tests appropriate to the materials or products involved.

11. Under the National classifications, lining systems which can be effectively tested for ‘surface spread of flame’ are rated for performance by reference to the method specified in BS 476- 7:1997 (or 1987 or 1971) Fire tests on building materials and structures. Method of test to determine the classification of the surface spread of flame of products under which materials or products are classified 1, 2, 3 or 4 with Class 1 being the highest.

Under the European classifications, lining systems are classified in accordance with BS EN 13501-1:2002 Fire classification of construction products and building elements, Part 1- Classification using data from reaction to fire tests. Materials or products are classified as A1, A2, B, C, D, E or F, with A1 being the highest. When a classification includes ‘s3, d2’, it means that there is no limit set for smoke production and/or flaming droplets/particles.

12. To restrict the use of materials which ignite easily, which have a high rate of heat release and/ or which reduce the time to flashover, maximum acceptable ‘fire propagation’ indices are specified, where the National test methods are being followed. These are determined by reference to the method specified in BS 476-6:1989 or 1981. Index of performance (I) relates to the overall test performance, whereas sub-index (ii) is derived from the first three minutes of test.

13. The highest National product performance classification for lining materials is Class 0. This is achieved if a material or the surface of a composite product is either:

a. composed throughout of materials of limited combustibility; or

b. a Class 1 material which has a fire propagation index (I) of not more than 12 and sub-index (ii) of not more than 6.

Note: Class 0 is not a classification identified in any British Standard test.

14. Composite products defined as materials of limited combustibility (see paragraph 9 and Table A7) should in addition comply with the test requirement appropriate to any surface rating specified in the guidance on requirements B2, B3 and B4.

15. The notional performance ratings of certain widely used generic materials or products are listed in Table A8 in terms of their performance in the traditional lining tests BS 476-6:1989 and BS 476-7:1997 or in accordance with BS EN 13501 -1:2002.

16. Results of tests on proprietary materials are frequently given in literature available from manufacturers and trade associations.

Any reference used to substantiate the surface spread of flame rating of a material or product should be carefully checked to ensure that it is suitable, adequate and applicable to the construction to be used. Small differences in detail, such as thickness, substrate, colour, form, fixings, adhesive etc, may significantly affect the rating.

Thermoplastic Materials

17. A thermoplastic material means any synthetic polymeric material which has a softening point below 200°C if tested to BS EN ISO 30 6:2004 method Al 20 Plastics — Thermoplastic materials – Determination of Vicat softening temperature. Specimens for this test may be fabricated from the original polymer where the thickness of material of the end product is less than 2.5mm.

18. A thermoplastic material in isolation can not be assumed to protect a substrate when used as a lining to a wall or ceiling. The surface rating of both products must therefore meet the required classification. If, however, the thermoplastic material is fully bonded to a non- thermoplastic substrate, then only the surface rating of the composite will need to comply.

19. Concessions are made for thermoplastic materials used for window glazing, rooflights, and lighting diffusers within suspended ceilings, which may not comply with the criteria specified in paragraphs 11 to 16. They are described in the guidance on requirements B2 and B4.

20. For the purposes of the requirements B2 and B4 thermoplastic materials should either be used according to their classification 0-3, under the BS 476-6:1989 and BS 476-7:1997 tests as described in paragraphs 11 to 16, (if they have such a rating), or they may be classified TP(a) rigid, TP(a) flexible, or TP(b) according to the following methods:

TP(a) rigid:

i. Rigid solid pvc sheet;

ii. Solid (as distinct from double- or multiple-skin) polycarbonate sheet at least 3mm thick;

iii. Multi-skinned rigid sheet made from unplasticised pvc or polycarbonate which has a Class 1 rating when tested to BS 476-7:1997 or 1971 or 1987; and

iv. Any other rigid thermoplastic product, a specimen of which (at the thickness of the product as put on the market), when tested to BS 2782:1 970 as amended in 1974: Method 508A Rate of burning (Laboratory method), performs so that the test flame extinguishes before the first mark and the duration of flaming or afterglow does not exceed five seconds following removal of the burner.

TP(a) flexible:

Flexible products not more than 1 mm thick which comply with the Type C requirements of BS 5867-2:1980 Specification for fabrics for curtains and drapes — Flammability requirements when tested to BS 5438:1989 Methods of test for flammability of textile fabrics when subjected to a small igniting flame applied to the face or bottom edge of vertically oriented specimens, Test 2, with the flame applied to the surface of the specimens for 5, 15, 20 and 30 seconds respectively, but excluding the cleansing procedure; and

TP(b):

i. Rigid solid polycarbonate sheet products less than 3mm thick, or multiple-skin polycarbonate sheet products which do not qualify as TP(a) by test; or

ii. Other products which, when a specimen of the material between 1.5 and 3mm thick is tested in accordance with BS 2782:1970, as amended in 1974: Method 508A, has a rate of burning which does not exceed 50mm/minute.

Note: If it is not possible to cut or machine a 3mm-thick specimen from the product then a 3mm test specimen can be moulded from the same material as that used for the manufacture of the product.

Note: Currently, no new guidance is possible on the assessment or classification of thermoplastic materials under the European system since there is no generally accepted European test procedure and supporting comparative data.

Fire test methods

21. A guide to the various test methods in BS 476 and BS 2782 is given in PD 6520 Guide to fire test methods for building materials and elements of construction (available from the British Standards Institution).

A guide to the development and presentation of fire tests and their use in hazard assessment is given in BS 6336:1998 Guide to development and presentation of fire tests and their use in hazard assessment.

Application of the fire resistance standards in table A2:

a. Where one element of structure supports or carries or gives stability to another, the fire resistance of the supporting element should be no less than the minimum penod of fire resistance for the other element (whether that other element is loadbearing or not).

There are circumstances where it may be reasonable to vary this principle, for example:

i. where the supporting structure is in the open air, and is not likely to be affected by the fire in the building; or

ii. where the supporting structure is in a different compartment, with a fire- separating element (which has the higher standard of fire resistance) between the supporting and the separated

structure; or

iii. where a plant room on the roof needs a higher fire resistance than the elements of structure supporting it.

b. Where an element of structure forms part of more than one building or compartment, that element should be constructed to the standard of the greater of the relevant provisions.

c. Although most elements of structure in a single storey building may not need fire resistance (see the guidance on requirement B3, paragraph 4.4(a)), fire resistance will be needed if the element:

i. is part of (or supports) an external wall and there is provision in the guidance on requirement B4 to limit the extent of openings and other unprotected areas in the wall; or

ii. is part of (or supports) a compartment wall, including a wall common to two or more buildings, or a wall between a dwellinghouse and an attached or integral garage; or

iii. supports a gallery.

For the purposes of this paragraph, the ground storey of a building which has one or more basement storeys and no upper storeys, may be considered as a single-storey building[for the purposes of part B of the Approved Documents] - A building consisting of a ground storey only. (A separated part which consists of a ground storey only, with a roof to which access is only provided for repair or maintenance, may be treated as a single storey building.) Basements are not included in counting the number of storeys in a building. . The fire resistance of the basement storeys should be that appropriate to basements.

Appendix B: Fire doors

1. All fire doors should have the appropriate performance given in Table B1 either:

a. by their performance under test to BS 476-22 Fire tests on building materials and structures. Methods for determination of the fire resistance of non-!oadbearing elements of construction, in terms of integrity for a period of minutes, e.g. FD3O. A suffix (S) is added for doors where restricted smoke leakage at ambient temperatures is needed; or

b. as determined with reference to Commission Decision 2000/367/EC of 3 May 2000 implementing Council Directive 89/106/EEC as regards the classification of the resistance to fire performance of construction products, construction works and parts thereof. All fire doors should be classified in accordance with BS EN 13501-2:2003 Fire classification of construction products and building elements. Classification using data from fire resistance tests (excluding products for use in ventilation systems). They are tested to the relevant European method from the following:

BS EN 1634-1:2008 Fire resistance and smoke control tests for door and shutter assemblies, openable windows and elements of building hardware. Fire resistance tests for doors, shutters and openable windows;

BS EN 1634-2:2008 Fire resistance and smoke control tests for door and shutter assemblies, openable windows and elements of building hardware. Fire resistance characterisation test for elements of building hardware;

BS EN 1634-3:2004 Fire resistance and smoke control tests for door and shutter assemblies, openable windows and elements of building hardware. Smoke control test for door and shutter assemblies.

The performance requirement is in terms of integrity (E) for a period of minutes. An additional classification of Sa is used for all doors where restricted smoke leakage at ambient temperatures is needed.

The requirement (in either case) is for test exposure from each side of the door separately.

Any test evidence used to substantiate the fire resistance rating of a door or shutter should be carefully checked to ensure that it adequately demonstrates compliance and is applicable to the adequately complete installed assembly. Small differences in detail (such as glazing apertures, intumescent strips, door frames and ironmongery etc.) may significantly affect the rating.

Note 1: The latest version of any standard may be used provided that it continues to address the relevant requirements of the Regulations.

Note 2: Until such time that the relevant harmonised product standards are published, for the purposes of meeting the Building Regulations, products tested in accordance with BS EN 1634-1 (with or without pre-fire test mechanical conditioning) will be deemed to have satisfied the provisions provided that they achieve the minimum fire resistance in terms of integrity, as detailed in Table B1.

2. Fire doors serving an attached or integral garage should be fitted with a self-closing device[for the purposes of part B of the Approved Documents] - A device which is capable of closing the door from any angle and against any latch fitted to the door. .

3. Unless shown to be satisfactory when tested as part of a fire door[for the purposes of part B of the Approved Documents] - A door or shutter, provided for the passage of persons, air or objects, which together with its frame and furniture as installed in a building, is intended (when closed) to resist the passage of fire and/or gaseous products of combustion, and is capable of meeting specified performance criteria to those ends. (It may have one or more leaves, and the term includes a cover or other form of protection to an opening in a fire-resisting wall or floor, or in a structure surrounding a protected shaft.) assembly, the essential components of any hinge on which a fire door is hung should be made entirely from materials having a melting point of at least 800°C.

4. Tables Al and A2 set out the minimum periods of fire resistance for the elements of structure to which performance of some doors is linked. Table A4 sets out limitations on the use of uninsulated glazing in fire doors.

5. BS 821 4:1990 gives recommendations for the specification, design, construction, installation and maintenance of fire doors constructed with non-metallic door leaves.

Guidance on timber fire-resisting doorsets, in relation to the new European test standard, may be found in Timber fire-resisting doorsets: maintaining performance under the new European test standard published by TRADATimber Research and Development Association. A trade association with a strong reputation for research and publication on all things timber (Timber Research and Development Association).

Guidance for metal doors is given in Code of practice for fire-resisting metal doorsets published by the DSMA (Door and Shutter Manufacturers’ Association) in 1999.

6. Hardware used on fire doors can significantly affect performance in fire. Notwithstanding the guidance in this Approved Document guidance is available in Hardware for fire and escape doors published by the Builders’ Hardware Industry Federation.

Appendix C: Methods of measurement

1. Some form of measurement is an integral part of many of the provisions in this document. Diagram C1 shows how the height of the top storey should be measured.

Appendix D: Purpose groups

1. Many of the provisions in this document are related to the use of the building. The use classifications are termed purpose groups and represent different levels of hazard. They can apply to a whole building, or (where a building is compartmented) to a compartment in the building, and the relevant purpose group should be taken from the main use of the building or compartment.

2. Table D1 sets out the purpose group classification.

Note: This is only of relevance to this Approved Document.

Ground movement (Requirement A2b)

1.9 There may be known or recorded conditions of ground instability, such as that arising from landslides, disused mines or unstable strata which, if ignored, can have a devastating effect on the safety of a building and its environs. Such conditions should be taken into account in the design of the building and its foundations. Attention is drawn to DOE Planning Policy Guidance Note 14 Development on unstable land (obtainable from The Stationery Office), which sets out the broad planning and technical issues relating to development on unstable land.

The Department has also sponsored a series of reviews aimed at determining the scale and nature of problems arising from mining instability, natural underground cavities and adverse foundation conditions. Databases of both subsidence incidents and subsidence potential produced from these reviews are available from the following licence holders:

British Geological Survey, Sir Kingsley Dunham Centre, Keyworth, Nottingham NG12 5GG.

Landmark, 7 Abbey Court, Eagle Way, Exeter, Devon EX2 7HY.

Peter Brett Associates, 16 Westcote Road, Reading, Berkshire RG2O 2DE.

Catalytic Data Ltd, The Spinney, 19 Woodlands Road, Bickley, Kent BRI 2AD.

The reports from these reviews, which include 1:250,000 scale maps showing the distribution of the physical constraints, are available from the following organisations:

Arup Geotechnics, 1991. Review of mining instability in Great Britain.

Obtainable from Arup Geotechnics, Bede House, All Saints, Newcastle-upon-Tyne NE1 2EB. Applied Geology Ltd, 1994. Review of instability due to natural underground cavities in Great Britain.

Obtainable from Kennedy & Donkin Ltd,

14 Calthorpe Road, Edgbaston, Birmingham

B15 1TH.

Wimpey Environmental Ltd, and National House Building Council, 1995. Foundation conditions in Great Britain, a guide for planners and developers. Obtainable from ESNR International Ltd, 16 Frogmore Road, Hemel Hempstead, Hertfordshire HP3 9RW. 

Section 2A: Basic requirements for stability

2A1 This section must be used in conjunction with sections 2B and 2C and its principles relate to all forms of low-rise residential buildings.

2A2 Adequate provision shall be made to ensure that the building is stable under the likely imposed and wind loading conditions. This will commonly necessitate meeting the following requirements:

a. That the overall size and proportioning of the building are limited in accordance with the specific guidance for each form of construction.

b. That a suitable layout of walls (both internal and external) forming a robust 3 dimensional box structure in plan is constructed with restriction on the maximum size of cells measured in accordance with the specific guidance for each form of construction.

c. That the internal and external walls are adequately connected either by masonry bonding or by using mechanical connections.

d. That the intermediate floors and roof are of such construction and interconnection with the walls that they provide local support to the walls and also act as horizontal diaphragms capable of transferring the wind forces to buttressing elements of the building.

Note: A traditional cut timber roof (i.e. using rafters, purlins and ceiling[for the purposes of part B of the Approved Documents] - A part of a building which encloses and is exposed overhead in a room, protected shaft or circulation space. (The soffit of a rooflight is included as part of the surface of the ceiling, but not the frame. An upstand below a rooflight would be considered as a wall.) joists) generally has sufficient built in resistance to instability and wind forces (e.g. from hipped ends, tiling battensNarrow strips of wood. Roof battens are narrow strips used to fix slates and tiles. Also used for tile and slate hanging on walls and rain screens, rigid sarkinga waterproof layer in a roof which acts as backup protection in case the main layer fails. Usually a membrane or board and usually situated between roof laths and joists. or the like). However, the need for diagonal rafter bracing equivalent to that recommended in BSBritish Standard 5268-3:1998 or Annex H of BS 81 03-3:1996 for trussed raftera triangulated, usually prefabricated roof beamSubstantial, usually horizontal structural member. roofs should be considered especially for single-hipped and non-hipped roofs of greater than 40° pitch to detached houses.

Note here that the Approved documents are heavily skewed in favour of masonry construction. With timber frame or SIPsStructural Insulated Panels - prefabricated (usually in a factory) timber panels often forming part of an integrated building system and aimed at fast site erection. see more on SIPs or any other framing system there is a great deal more flexibility of layout and the notion of a box structure with ‘cells’ is much less important.

Most of the rest of this page is about masonry construction.

Section 2B: Sizes of certain timber members in floors and roofs for dwellings. Areas at risk from house longhorn beetle

Sizing of members

If you are considering using a frame construction such as post and beam then everything will need calculating from scratch by a structural engineer

2B1 Guidance on the sizing of certain members in floors and roofs is given in ‘Span tables for solid timber members in floors, ceilings and roofs (excluding trussed rafter roofs) for dwellings’, published by TRADATimber Research and Development Association. A trade association with a strong reputation for research and publication on all things timber, available from Chiltern House, Stocking Lane, Hughenden Valley, High Wycombe, Bucks HP14 4ND.

Alternative guidance is available in BS 5268-2:2002 Code of practice for permissible stress design, materials and workmanship, BS 5268-3:1998, Code of practice for trussed rafter roofs and BS 81 03-3:1996 Structural design of low-rise buildings, Code of Practice for timber floors and roofs for dwellings.

Span tables for timber floor, ceiling and roof members used to be published as part of the Approved Documents but were then withdrawn. The archived version of these tables are still available and are almost identical to the ones published by TRADA (since wood has not changed a great deal over the centuries). They are in the repealed 1992 Approved Documents. Useful for getting an idea of what is required. For more up to date information click here for a google search

House longhorn beetle

2B2 In the geographical areas specified in Table 1, softwood timber for roof construction or fixed in the roof space, including ceiling joists within the void spaces of the roof, should be adequately treated to prevent infestation by the house longhorn beetle (Hylotrupes bajulus L.).

Guidance on suitable preservative treatments is given within the British Wood Preserving and Damp-Proofing Associationa body which has now split into the Property Care Association and the Wood Protection Association’s Manual (2000 revision), available from 1 Gleneagles House, Vernongate, South Street, Derby DE1 1 UP

Section 2C: Thickness of walls in certain small buildings

Application

2C1 This section applies to the following building types:

a. residential buildings of not more than three storeys;

b. small single-storey[for the purposes of part B (fire) of the Approved Documents to the Building Regulations] this means a. any gallery[for the purposes of part B of the Approved Documents] - A raised area or platform around the sides or at the back of a room which provides extra space. Habitable room A room used, or intended to be used, for dwellinghouse[for the purposes of part B of the Approved Documents] - A unit of residential accommodation occupied (whether or not as a sole or main residence): a. by a single person or by people living together as a family b. by not more than six residents living together as a single household, including a household where care is provided for residents. (See also paragraphs 0.22 and 0.23.) Dwellinghouse does not include a flat or a building containing a flat. purposes (including; for the purposes of Part B, a kitchen, but not a bathroom). if its area is more than half that of the space into which it projects; and b. a roof, unless it is accessible only for maintenance and repair. non-residential buildings;

c. small buildings forming annexes to residential buildings (including garages and outbuildings).

Wall types

2C2 Only the types of wall given in Table 2, which must extend to the full storey height, and parapet walls are considered in this section.

The use of this section

2C3 When using this section it should be noted that:

a. this section must be used in conjunction with Section 2A;

b. if wall thickness is to be determined according to paragraphs 2C5 to 2C13, all appropriate design conditions given in this section must be satisfied;

c. walls should comply with the relevant requirements of BS 5628: Part 3:2001, except as regards the conditions given in paragraphs 2C4 and 2C14 to 2C38;

d. in formulating the guidance of this section the worst combination of circumstances likely to arise was taken into account. If a requirement of this part is considered too onerous in a particular case it may be appropriate to consider a minor departure on the basis of judgement and experience, or to show adequacy by calculation in respect of the aspect of the wall which is subject to the departure rather than for the entire wall;

e. the guidance given is based upon the compressive strengths of bricks and blocks being not less than indicated in Tables 6 and 7.

BS 5628-1:1992 gives design strengths for walls where the suitability for use of masonry units of other compressive strengths is being considered.

Conditions relating to the building of which the wall forms part

2C4 This Section applies only to buildings having proportions within the following parameters (see Diagrams 1 and 2):

a. residential buildings of not more than three storeys:

i. the maximum height of the building measured from the lowest finished ground level adjoining the building to the highest point of any wall or roof should not be   greater than 15m, subject to the limits of paragraph 2C16;

ii. the height of the building H should not exceed twice the least width of the building W1;

iii. the height of the wing H2 should not exceed twice the least width of the wing W2 where the projection P exceeds twice the width W2;

b. small single-storey non-residential buildings:

height H should not exceed 3m and W (being the greatest length or width of the building) should not exceed 9m (see Diagram 2), subject to the limits of paragraph 2C16; 

c. annexes: height H as variously indicated in Diagram 2 should not exceed 3m, subject to the limits of paragraph 2C16.

Thickness of walls

2C5 General wall thickness may be determined according to this section provided:

a. conditions relating to the building of which the wall forms part (see paragraphs 2C4, 2C14 to 2C16, 2C38); and

b. conditions relating to the wall (see paragraphs 2C17 to 2C37) are met. (See Diagram 3.)

2C6 Solid external walls, compartment[for the purposes of part B of the Approved Documents] - (fire) A building or part of a building, comprising one or more rooms, spaces or storeys, constructed to prevent the spread of fire to or from another part of the same building, or an adjoining building. (A roof space above the top storey of a compartment is included in that compartment.) (See also ‘Separated part’.) walls and separating walls in coursed brickwork or blockwork: Solid walls constructed of coursed brickwork or blockwork should be at least as thick as 1/16 of the storey height. Further requirements are given in Table 3.

2C7 Solid external walls, compartment walls and separating walls in uncoursed stone, flints, etc.: The thickness of walls constructed in uncoursed stone, flints, clunchesusually soft, lime based building stones, bricks or other burnt or vitrified material should not be less than 1.33 times the thickness determined by paragraph 2C6.

see the section on ‘How much insulation? Increasing levels of insulation are having a bearing on wall thickness and construction, especially with cavity[for the purposes of part B of the Approved Documents] - A space enclosed by elements of a building (including a suspended ceiling) or contained within an element, but not a room, cupboard, circulation space, protected shaft or space within a fluepipe to conduct gas, typically ventilation air or boiler exhaust. see Flue, chute, duct, pipe or conduit. walls

2C8 Cavity walls in coursed brickwork or blockwork: All cavity walls should have leaves at least 90mm thick and cavities at least 50mm wide. The wall ties should have a horizontal spacing of 900mm and a vertical spacing of 450mm, which is equivalent to 2.5 ties per square metre. Wall ties should also be provided, spaced not more than 300mm apart vertically, within a distance of 225mm from the vertical edges of all openings, movement joints and roof verges. For selection of wall ties for use in a range of cavity widths refer to Table 5. For specification of cavity wall ties refer to paragraph 2C1 9.

For external walls, compartment walls and separating walls in cavity construction, the combined thickness of the two leaves plus 10mm should not be less than the thickness determined by paragraph 2C6 and Table 3 for a solid wall of the same height and length.

In some cases such as PassivhausSee more on the Passivhaus standard. The PassivHaus Institute has pioneered a standard for low energy buildings. It includes very low energy usage and ways of achieving this. The word is derived from the idea of buildings which are fundamentally low energy and passive solar heated rather than using extra gadgets to heat them. See Passivhaus for the UK branch of the organisation. construction, wall ties may need to be of an insulating type to avoid causing a cold bridge

2C9 Walls providing vertical support to other walls: Irrespective of the material used in the construction, a wall should not be less in thickness than any part of the wall to which it gives vertical support.

2C10 Internal load-bearing walls in brickwork or blockwork (except compartment walls or separating walls): All internal load-bearing walls should have a thickness not less than:

except for a wall in the lowest storey of a three storey building, carrying load from both upper storeys, which should have a thickness as determined by the equation or 140mm whichever is the greatest.

2C11 Parapet walls: The minimum thickness and maximum height of parapet walls should be as given in Diagram 4.

2C12 Single leaves of certain external walls: The single leaf of external walls of small single storey non-residential buildings and of annexes need be only 90mm thick, notwithstanding paragraphs 2C38.

2C13 Modular bricks and blocks: Where walls are constructed of bricks or blocks having modular dimensions derived from BS 6649:1985, wall thicknesses prescribed in this section which derive from a dimension of brick or block may be reduced by an amount not exceeding the deviation from work size permitted by a British Standard relating to equivalent sized bricks or blocks made of the same material.

2C14 Maximum floor area: The guidance of this section assumes that no floor enclosed by structural walls on all sides exceeds 70m², and that no floor without a structural wall on one side exceeds 36m². (See Diagram 5.)

2C15 Imposed loadsThe loads assumed to be produced by the intended occupancy or use, including the weight of movable partitions, distributed, concentrated, impact, inertia and snow loads, but excluding wind loads. on roofs, floors and ceilings: The design considerations given in this section are intended to be adequate for the imposed loads given in Table 4.

2C16 Maximum height of buildings: The design guidance in this section is based on BS 6399-2:1997. The maximum heights of buildings given in Table c of Diagram 7 correlate to various site exposure conditions and wind speeds. A map showing wind speeds is given in Figure 1 of Diagram 6.

Conditions relating to the wall

2C17 Maximum allowable length and height of the wall: This section does not deal with walls longer than 12m, measured from centre to centre of buttressing walls, piers or chimneys providing restraint, or with walls exceeding 1 2m in height (see also Table 3).

2C18 Rules of measurement for heights of walls and storeys: The height of a wall or a storey should be measured in accordance with the rules in Diagram 8.

Construction materials and workmanship

2C19 Wall ties: Wall ties should either comply with BS 1243, DD 140, or BS EN 845-1 and should be material references 1 or 3 in BS EN 845 Table A 1 austenitic stainless steel. Wall ties should be selected in accordance with Table 5 of this Approved DocumentThese are a part of the Building Regulations which ensure, if you follow them, that your plans will be automatically approved. The full set of the documents is available here.

In some cases such as Passivhaus construction, wall ties may need to be of an insulating type to avoid causing a cold bridge

2C20 Masonry units: Walls should be properly bonded and solidly put together with mortar and constructed of masonry units conforming to:

a. clay bricks or blocks to BS 3921 :1985 or BS 6649:1985 or BS EN 771-1;

b. calcium silicate bricks to BS 187:1978 or BS 6649:1985 or BS EN 771-2;

c. concrete bricks or blocks to BS 6073-1 :1981 or BS EN 771-3 or -4;

d. square dressed natural stone to the appropriate requirements described in BS EN 771-6 or BS 5628-3:2001;

e. manufactured stone to BS 6457:1 984 or BS EN 771-5.

2C21 Compressive strength of masonry units: Minimum compressive strength requirements for masonry units according to BS EN Standards are given in Diagram 9, where the masonry units indicated for Conditions A, B and C should have declared compressive strengths of not less than the values given in Table 6. Normalised compressive strengths for block sized clay and calcium silicate masonry units not complying with brick dimensional format are given in Table 7. 

2C22 Mortar: Mortar should be:

a. 

i. Mortar designation (iii) according to BS BS 5628-3:2001.

ii. Strength class M4 according to BS EN 998-2.

iii. 1:1:5 or 6 CEM 1, lime and fine aggregategravel, crushed stone and other coarse material used in concrete or as hardcore measured by volume of dry materials, or

b. of equivalent or greater strength and durability to the specification in a. above.

Loading on walls

2C23 Maximum span of floors: The maximum span for any floor supported by a wall is 6m where the span is measured centre to centre of bearing (see Diagram 10).

2C24 Other loading conditions:

a. Vertical loading on walls should be distributed. This may be assumed for concrete floor slabs, precast concrete floors, and timber floors designed in accordance with section 2B, and where the bearing length for lintels is 150mm or greater. Where a lintel has a clear span of 1200mm or less the bearing length may be reduced to 100mm.

b. Differences in level of ground or other solid construction between one side of the wall and the other should be less than 4 times the thickness of the wall as shown in Diagram 11.

c. The combined dead and imposed loadThe load assumed to be produced by the intended occupancy or use, including the weight of movable partitions, distributed, concentrated, impact, inertia and snow loads, but excluding wind loads. should not exceed 7OkN/m at base of wall (see Diagram 11).

d. Walls should not be subjected to lateral load other than from wind, and that covered by paragraph 2C24(b). 

End restraint

2C25 Vertical Lateral Restraint to Walls

The ends of every wall should be bonded or otherwise securely tied throughout their full height to a buttressing wall, pierA member which forms an integral part of a wall, in the form of a thickened section at intervals along the wall, so as to afford lateral support to the wall to which it is bonded or securely tied. or chimney. Long walls may be provided with intermediate buttressing walls, piers or chimneys dividing the wall into distinct lengths within each storey; each distinct length is a supported wall for the purposes of this section. The intermediate buttressing walls, piers or chimneys should provide lateral restraint to the full height of the supported wall, but they may be staggered at each storey.

2C26 Buttressing Walls

If the buttressing wall is not itself a supported wall its thickness T2 should not be less than:

a. half the thickness required by this section for an external or separating wall[for the purposes of part B (fire) of the Approved Documents] - A wall or part of a wall which is common to adjoining buildings, and constructed to meet the requirements of regulation B3(2) [for the purposes of part C (sound) of the Approved Documents] - Wall that separates adjoining dwelling-houses, flats or rooms for residential purposes. of similar height and length less 5mm; or

b. 75mm if the wall forms part of a dwelling house and does not exceed 6m in total height and lOm in length; and

c. 90mm in other cases.

The length of the buttressing wall should be at least 1/6 of the overall height of the supported wall and be bonded or securely tied to the supporting wall and at the other end to a buttressing wall, pier or chimney.

The size of any opening in the buttressing wall should be restricted as shown in Diagram 12.

2C27 Design criteria for piers and chimneys providing restraint:

a. piers should measure at least 3 times the thickness of the supported wall and chimneys twice the thickness, measured at right angles to the wall. Piers should have a minimum width of 190mm (see Diagram 13);

bear in mind the problems of insulating a masonry chimney on an external wall. see Chimneys

b. the sectional area on plan of chimneys (excluding openings for fireplaces and fluespipe to conduct gas, typically ventilation air or boiler exhaust. see more on Flues ) should be not less than the area required for a pier in the same wall, and the overall thickness should not be less than twice the required thickness of the supported wall (see Diagram 13).

Openings, recesses, overhangs and chases

2C28 General:

The number, size and position of openings and recesses should not impair the stability of a wall or the lateral restraint afforded by a buttressing wall to a supported wall. Construction over openings and recesses should be adequately supported.

2C29 Dimensional criteria for openings and recesses: The dimensional criteria are given in Diagram 14 and Table 8.

No openings should be provided in walls below ground floor except for small holes for services and ventilation, etc. which should be limited to a maximum area of 0.1 m²at not less than 2m centres.

2C30 Chases:

a. vertical chases should not be deeper than 1/3 of the wall thickness or, in cavity walls, 1/3 of the thickness of the leaf;

b. horizontal chases should not be deeper than 1/6 of the thickness of the leaf of the wall;

c. chases should not be so positioned as to impair the stability of the wall, particularly where hollow blocks are used.

2C31 Overhangs:

The amount of any projection should not impair the stability of the wall. 

Lateral support by roofs and floors

2C32  A wall in each storey of a building should extend to the full height of that storey, and have horizontal lateral supports to restrict movement of the wall at right angles to its plane.

2C33  Floors and roofs should:

a. act to transfer lateral forces from walls to buttressing walls, piers or chimneys; and

b. be secured to the supported wall by connections specified in paragraphs 2C34 and 2C35.

2C34  The requirements for lateral restraint of walls at roof and floor levels are given in Table 9 and guidance on satisfying the requirements is given in paragraphs 2C35 and 2C36.

2C35  Walls should be strapped to floors above ground level, at intervals not exceeding 2m and as shown in Diagram 15 by tension straps conforming to BS EN 845-1. For corrosion resistance purposes, the tension straps should be material reference 14 or 16.1 or 16.2 (galvanised steel) or other more resistant 

specifications including material references 1 or 3 (austenitic stainless steel). The declared tensile strength of tension straps should not be less than 8kN.

Tension straps need not be provided:

a. in the longitudinal direction of joists in houses of not more than 2 storeys, if the joists are at not more than 1 .2m centres and have at least 90mm bearing on the supported walls or 75mm bearing on a timber wall-plate at each end, and

b. in the longitudinal direction of joists in houses of not more than 2 storeys, if the joists are carried on the supported wall by joist hangers in accordance with BS EN 845-1 of the restraint type described in BS 5628-1 and shown in Diagram 15(c), and are incorporated at not more than 2m centres, and

c. when a concrete floor has at least 90mm bearing on the supported wall (see Diagram 15(d)), and

d. where floors are at or about the same level on each side of a supported wall, and contact between the floors and wall is either continuous or at intervals not exceeding 2m. Where contact is intermittent, the points of contact should be in line or nearly in line on plan (see Diagram 15(e)).

2C36 Gable walls should be strapped to roofs as shown in Diagram 16(a) and (b) by tension straps as described in 2C35.

Vertical strapping at least 1 m in length should be provided at eaves level at intervals not exceeding 2m as shown in Diagram 16(c) and (d). Vertical strapping may be omitted if the roof:

a. has a pitch of 15° or more, and

b. is tiled or slated, and

c. is of a type known by local experience to be resistant to wind gusts, and

d. has main timber members spanning onto the supported wall at not more than 1 .2m centres. 

Interruption of lateral support

2C37  Where an opening in a floor or roof for a stairway or the like adjoins a supported wall and interrupts the continuity of lateral support, the following conditions should be satisfied for the purposes of Section 2C:

a. the maximum permitted length of the opening is to be 3m, measured parallel to the supported wall, and

b. where a connection is provided by means other than by anchor, this should be provided throughout the length of each portion of the wall situated on each side of the opening, and

c. where a connection is provided by mild steel anchors, these should be spaced closer than 2m on each side of the opening to provide the same number of anchors as if there were no opening, and

d. there should be no other interruption of lateral support.

Small single-storey non-residential buildings and annexes

2C38  Size and proportion

(i) General

The guidance given applies in the following circumstances:

a. The floor area of the building or annexe does not exceed 36m².

b. The walls are solidly constructed in brickwork or blockwork using materials which comply with paragraphs 2C19 to 2C22.

c. Where the floor area of the building or annexe exceeds 10m² the walls have a mass of not less than 130kg/rn2.

Note: There is no surface mass limitation recommended for floor areas of 10m² or less.

d. Access to the roof is only for the purposes of maintenance and repair.

e. The only lateral loads are wind loads.

f. The maximum length or width of the building or annexe does not exceed 9m.

g. The height of the building or annexe does not exceed the lower value derived from Diagram 2.

h. The roof is braced at rafter level, horizontally at eaves level and at the base of any gable by roof decking, rigid sarking or diagonal timber bracing, as appropriate, in accordance with BS 5268-3. 

i. Walls are tied to the roof structure vertically and horizontally in accordance with paragraphs 2C32 to 2C36 and with horizontal lateral restraint at roof level in accordance with paragraph (iv) below.

j. The roof structure of an annexe is secured to the structure of the main building at both rafter and eaves level. 

(ii) Size and location of openings

One or two major openings not more than 2.1 m in height are permitted in one wall of the building or annexe only. The width of a single opening or the combined width of two openings should not exceed 5m.

The only other openings permitted in a building or annexe are for windows and a single leaf door. The size and location of these openings should be in accordance with Diagram 17.

(iii) Wall thickness and recommendations for piers

The walls should have a minimum thickness of 90mm.

Walls which do not contain a major opening but exceed 2.5m in length or height should be bonded or tied to piers for their full height at not more than 3m centres as shown in Diagram 1 8a. Walls which contain one or two major openings should in addition have piers as shown in Diagrams 1 8b and 1 Bc. Where ties are used to connect piers to walls they should be flat, 20mm x 3mm in cross section, be in stainless steel in accordance with clause 2C19, be placed in pairs and be spaced at not more than 300mm centre vertically. 

(iv) Horizontal lateral restraint at roof level Walls should be tied horizontally at no more than 2m centres to the roof structure at eaves level, base of gables and along roof slopes as shown in Diagram 19 with straps fixed in accordance with paragraphs 2C35 and 2C36. Where straps cannot pass through a wall they should be adequately secured to the masonry using suitable fixings. Isolated columns should also be tied to the roof structure (see Diagram 19).

Section 2D: Proportions for masonry chimneys above the roof surface

Height to width relationship

2D1   Where a chimney is not adequately supported by ties or securely restrained in any way, its height if measured from the highest point of intersection with the roof surface, gutter, etc. should not exceed 4.5W, provided the density of the masonry is greater than 1500kg/m³, where:

W is the least horizontal dimension of the chimney measured at the same point of intersection, and

Very tall chimneys can be supported with ties. Ask a structural engineer to specify the size of tie.

H is measured to the top of any chimney pot or other flue terminal (see Diagram 20). 

Section 2E: Foundations of plain concrete

Conditions relating to the ground

2E1  There should not be:

a. non-engineered fill (as described in BREBuilding Research Establishment. Digest 427) or wide variation in ground conditions within the loaded area; nor

b. weaker or more compressible ground at such a depth below the foundation as could impair the stability of the structure.

Design provisions

note that the concrete foundations used for Segal style construction are blocks of concrete rather than strips. This uses less concrete. see more under Groundworks | Foundations

2E2  The following design provisions relate to foundations:

a the foundations should be situated centrally under the wall;

b. for foundations in chemically aggressive soil conditions guidance in BS 8500-1 and BRE Special Digest 1 should be followed. In non-aggressive soils, concrete should be composed of Portland cementthe commonest form of cement to BS EN 197-1 and -2 and fine and coarse aggregate conforming to BS EN 12620 and the mix should comply with one of the following recommendations:

i. in proportion of 50kg of Portland cement to not more than 200kg (0.1 m³) of fine aggregate and 400kg (0.2m³) of coarse aggregate; or

ii. grade ST2 or grade GEN I concrete to BS 8500-2;

c. minimum thickness T of concrete foundation should be 150mm or P, whichever is the greater where P is derived using Table 10 and Diagram 23. Trench filltrench fill foundations are just that - fill the trench with concrete foundations may be used as an acceptable alternative to strip foundations;

d. foundations stepped on elevation should overlap by twice the height of the step, by the thickness of the foundation, or 300mm, whichever is greater (see Diagram 21).

For trench fill foundations the overlap should be twice the height of the step or 1 m, whichever is greater;

e. steps in foundations should not be of greater height than the thickness of the foundation (see Diagram 21);

f. foundations for piers, buttresses and chimneys should project as indicated in Diagram 22 and the projection X should never be less than the value of P where there is no local thickening of the wall.

Minimum width of strip foundations

2E3  The recommended minimum widths of foundations given in Table 10 may be used.

The table is applicable only within the strict terms of the criteria described within it.

Minimum depth of strip foundations

2E4  Except where strip foundations are founded on rock, the strip foundations should have a minimum depth of 0.45m to their underside to avoid the action of frost. This depth, however, will commonly need to be increased in areas subject to long periods of frost or in order to transfer the loading onto satisfactory ground.

In clay soils subject to volume change on drying (‘shrinkable clays’, with Plasticity Index greater than or equal to 10%), strip foundations should be taken to a depth where anticipated ground movements will not impair the stability of any part of the building taking due consideration of the influence of vegetation and trees on the ground. The depth to the underside of foundations on clay soils should not be less than O.75m, although this depth will commonly need to be increased in order to transfer the loading onto satisfactory ground.

Section 3: Wall cladding

General

3.1  Wall cladding presents a hazard if it becomes detached from the building. This section provides guidance on the support and fixing of wall cladding. An acceptable level of safety can be achieved by different means depending on the type and location of the cladding.

see also the section on rain screensthis is a (usually thin) outer cladding on a wall which prevents rain, snow, etc getting at the structure of the wall behind. see more on rain screens

The guidance given relates to all forms of cladding, including curtain walling and glass facades. It is not intended to provide guidance concerning the weather resistance of wall cladding which is included in Approved Document C, Site preparation and resistance to moisture, or guidance on resistance to spread of fire which is included in Approved Document B, Fire safety, or guidance in relation to sound insulation, which is included in Approved Document E, Resistance to the passage of sound.

Technical approach

3.2  The cladding will meet the safety requirement if:

a. the cladding is capable of safely sustaining and transmitting to the supporting structure of the building all dead, imposed and wind loads, and

b. the cladding is securely fixed to and supported by the structure of the building. This shall comprise both vertical support and horizontal restraint, and

c. provision is made, where necessary, to accommodate differential movement of the cladding and the supporting structure of the building, and

d. the cladding and its fixings (including any support components) are of durable materials; the design life of the fixings being not less than that of the cladding. Fixings shall be corrosion resistant and of a material type appropriate for the local environment.

Loading

3.3  Wind loading on the cladding should be derived from BS 6399-2:1997 with due consideration given to local increases in wind suction arising from funnelling of the wind through gaps between buildings. Guidance on funnelling effects is given in BRE Digest 436 Wind loading on buildings — Brief guidance for using BS 6399-2:1997 available from BRE, Bucknalls Lane, Garston, Watford, Herts WD2 7JR.

3.4  Where the cladding is required to support other fixtures, e.g. handrails, and fittings, e.g. antennae and signboards, account should be taken of the loads and forces arising from such fixtures and fittings.

3.5  Where the wall cladding is required to function as pedestrian guarding to stairs, ramps, vertical drops of 600mm or greater or as a vehicle barrier, then account should be taken of the additional imposed loading, as stipulated in Approved Document K, Protection from falling, collision and impact.

3.6  Where the wall cladding is required to safely withstand lateral pressures from crowds, an appropriate design loading is given in BS 6399 Part 1 and the Guide to Safety at Sports Grounds (4th Edition, 1997).

Fixings

3.7  The selection of fixings for supporting cladding should be determined from a

consideration of the proven performance of the fixing and the risks associated with the particular application. In this regard applications should be designated as being either non-redundant (where the failure of a single fixing could lead to the detachment of the cladding) or redundant (where failure or excessive movement of one fixing results in load sharing by adjacent fixings) and the required reliability of the fixing determined accordingly.

Note: Attention is drawn to the availability of anchors with an ETAEuropean Technical Approval (European Technical ApprovalA favourable technical assessment of the fitness for use of a construction product for an intended use, issued for the purposes of the Construction Products Directive by a body authorised by a Member State to issue European Technical Approvals for those purposes and notified by that Member State to the European Commission. ) gained in accordance with the requirements of ETAG 001 Guideline for European Technical Approval Metal Anchors for use in Concrete Parts 1-5, which cover both redundant and non-redundant applications, and Part 6 which covers ‘Anchors for multiple use in non-structural applications’ and which can effectively be regarded as covering redundant use. The UK definition of ‘multiple use’ is contained in an annexe to the ETAG Part 6 and is framed in such a way that all applications can be validated as to whether or not they conform to this category without calculation. All ETAG parts may be downloaded in English from www.eota.be.

3.8  The strength of fixings should be derived from tests using materials representative of the material into which the fixing is to be anchored, taking account of any inherent weaknesses that may affect the strength of the fixing, e.g. cracks in concrete due to shrinkage and flexure, or voids in masonry construction. The design loads will generally be available from the manufacturer’s test data determined from a European Technical Approval (ETA) or an extant British Standard.

Note: ETAS are available which cover use either in both cracked and non-cracked concrete or in non-cracked concrete only. Those which cover both cracked and non-cracked concrete allow higher loads for use in non-cracked than in cracked concrete. Guidance on how to determine whether a particular concrete section may be regarded as cracked or non-cracked without reverting to stress calculations is contained in ‘Use of anchors with European Technical Approvals. UK Guidance — Distinction between cracked and non-cracked concrete’. This is available on the BBA website www.bbacerts.co.uk click tab ‘ETA’.

Further guidance

3.9  The use of large panels of glass in cladding of walls and roofs where the cladding is not divided into small areas by load-bearing framing requires special consideration. Guidance is given in the following documents:

The Institution of Structural Engineers’ Report on ‘Structural use of glass in buildings’ dated 1999, available from 11 Upper BeIg rave Street, London SW1X 8BH.

‘Nickel sulfide in toughened glass’ published by the Centre for Window Cladding and Technology dated 2000.

3.10 Further guidance on cladding is given in the following documents:

The Institution of Structural Engineers’ Report on ‘Aspects of Cladding’ dated 1995.

The Institution of Structural Engineers’ Report on ‘Guide to the structural use of adhesives’ dated 1999.

BS 8297:2000 Code of practice for the design and installation of non-load-bearing pre-cast concrete cladding.

BS 8298:1994 Code of practice for the design and installation of natural stone cladding and lining.

3.11 Additional guidance on fixings is given in the following documents:

ETAG No. 001 1997 Guideline for European Technical Approvals of Metal Anchors for use in Concrete, European Organisation for Technical Approvals (EOTA), Brussels. All EOTA parts may be downloaded in English from www.eota.be.

English version published by the British Board of Agreement, P0 Box 195, Bucknalls Lane, Garston, Watford, Hertfordshire WD25 9BA.

Part 1 Anchors in general.

Part 2 Torque controlled anchors.

Part 3 Undercut anchors.

Part 4 Deformation controlled anchors.

Part 5 Bonded anchors.

Part 6 Metal anchors for redundant use in concrete for lightweight systems.

BS 5080-1:1993 Structural fixings in concrete and masonry. Method of test for tensile loading. CIRIAConstruction industry research and information association Report RP 566 Cladding Fixings: Good practice guidance, available from 6 Storey’s Gate, London SWIP 3AU.

CIRIA Reports C579 and C589 Retention of masonry facades — Best practice guide.

Guidance notes published by the Construction

Fixings Association, do Institute of Spring

Technology, Henry Street, Sheffield,

South Yorks S3 7EQ.

Guidance Note: Procedure for Site Testing Construction Fixings (1994).

Guidance Note: European Technical Approvals for Construction Fixings (1998).

Guidance Note: Anchor Selection (1995).

Guidance Note: Fixings and Fire (1998).

Guidance Note: Anchor Installation (1996).

Guidance Note: Bonded Anchors (1999).

Guidance Note: Heavy Duty Expansion

Anchors (1997).

Guidance Note: Fixings for Brickwork and

Blockwork (1997).

Guidance Note: Undercut Anchors (1998).

Guidance Note: Fixings and Corrosion (2002). 

Section 4: Roof covering

Materials

4.1  All materials used to cover roofs, including transparent or translucent materials, but excluding windows of glass in residential buildings with roof pitches of not less than 15°, shall be capable of safely withstanding the concentrated imposed loads upon roofs specified in BS 6399: Part 3.

Re-covering of roofs

4.2  The re-covering of roofs is commonly undertaken to extend the useful life of buildings. Roof structures may be required to carry underdrawing or insulation provided at a time later than their initial construction. This section provides guidance on determining whether such work to a roof constitutes a material alteration under the Building Regulations.

The planting of a living roof on an existing structure may well require a strengthening of the roof. Sedum roofs tend to be no heavier than normal roof coverings such as ballast or tiles but a turf roof which will usually require 150mm of soil will add quite a lot of extra weight

4.3  Where the work involves a significant change in the applied loading the structural integrity of the roof structure and the supporting structure should be checked to ensure that upon completion of the work the building is not less compliant with Requirement Al than the original building.

4.4  A significant change in roof loading is when the loading upon the roof is increased by more than 15%.

4.5  Where such checking of the existing roof structure indicates that the construction is unable to sustain any proposed increase in loading (e.g. due to overstressed members or unacceptable deflection leading to ponding), appropriate strengthening work or replacement of roofing members should be undertaken. This is classified as a material alteration.

4.6  In carrying out the checks mentioned in paragraph 4.3 an increase of stress in a structural member arising from increased loading does not necessarily indicate that the roof structure is less compliant than the original roof provided an adequate factor of safety is maintained.

4.7  Where work will significantly decrease the roof dead loading, the roof structure and its anchorage to the supporting structure should be checked to ensure that an adequate factor of safety is maintained against uplift of the roof under imposed wind loading.