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Internal linings

this clay plaster wall at the Denby Dale passivhaus was applied in 4 coats

this clay plaster wall at the Denby Dale passivhaus was applied in 4 coats. It has hemp reinforcement

wall and ceiling linings

There have been several fairly recent developments in dry lining boards for internal walls.

Traditional plasterboard is being challenged by other variations of gypsum based boards and also by clay based lining boards and wood based boards. Lining boards usually have to have a degree of fire resistance both structurally and with regard to the spread of flame (Building Regulations: Linings and Structure) and this limits the materials that can be used.

The problems with plasterboard have been to do with mining and processing the gypsum and also with the disposal of plasterboard because in normal land fill situations the calcium sulphate reacts with various acids also present in the land fill to produce sulphuric acid. Because of this, plasterboard must now be disposed of in special ‘toxic box’ sites designated by the local authority.

An added factor driving the change is that plasterboard has so little strength before it is fixed and damaged boards tend to litter many a building site so some of the newer boards tend to be less brittle and also tend to have a better finish.

Most of the newer boards come from northern Europe and are still being imported which adds to the embodied energy  and cost.

Dot and dab problems

For several decades now, the technique known as ‘dot and dab’ has been used for fixing plasterboard (and insulation backed plasterboard) to blockwork and brickwork. This has taken over from plastering the wall (which was the original way that drafts were prevented from entering through joints in masonry). The problem with dot and dab is that it leaves a narrow gap between the plasterboard and the wall structure and cold air can easily circulate around in this gap. The cold air gets in through the inevitable gaps, particularly perpends between the bricks and blocks. Also cold air enters at floor and eaves level and sometimes around window linings. This cold air is then much closer to the inside surface of the room.

reasons to build ecologicallyIn theory it is possible to try to seal all around the edge of each board but this seldom occurs for reasons of speed. The result is that an enormous number of houses have very reduced insulation. Also, theoretically it is possible to inject insulating foam into the gap and seal it but the problem with this is that it is very difficult to know exactly where the foam is going. If expanding foam is used to try to force it to fill all the voids then there is a risk it will over-expand and blow the plasterboard off the wall. In many cases the only remedy is to remove the plasterboard and plaster in the traditional way, possibly while at the same time adding internal insulation. See Wall Insulation

building regulations

Fire safety

With most forms of construction there will be implications concerning fire safety. These are covered in the Building Regulations and you can see examples of how to conform with these in Part B (Fire Safety)

Resistance to the passage of sound

The degree of sound insulation required within and between houses and flats is covered in Part E of the Approved Documents.


Sasmox is 85% Gypsum and 15% wood fibre which gives it more strength and better fixing properties. It has its own proprietary joint filler and does not need plastering. It comes from Finland.

Heraklith wood wool is a mixture of wood strands and cement which behaves well in fire and is also acoustically insulating. Made in Germany.

fermacell is a gypsum/celulose lining board made in Germany to a high ecological standard using recycled materials. See more information on fermacell

Claytec manufacture a clay based lining board and clay plasters.

Clayworks do clay plasters (and unfired clay blocks)


floor finishes

Perhaps the three most important green issues for floor finishes are –

  • that the materials they are made of should be sustainably sourced
  • that they are robust and can be repaired or refinished if damage occurs. (see Low maintenance design )
  • that they are attractive in themselves so that they don’t necessarily need a fitted carpet. Fitted carpets are one of the highest users of oil as they tend to get replaced every seven years on average

The opposite to the above is probably acrylic fitted carpets which have for a long time been used in the UK to effectively hide building defects such as rough, uneven, cold and drafty wooden floors and ill fitting skirting boards. The problems with this approach are heavy localised wear, difficulty in cleaning, harbouring of allergens and high embodied energy. A well laid, insulated floor (possibly heated) tends to be an attractive feature in itself which may only need a light rug to enhance it. This leads to flexibility in design. Localized wear is hardly a problem and can be easily repaired, – with the following caveats –

  • wood laminate flooring can only be easily sanded down if there is a sufficiently thick upper finish layer to sand at without going through to the layer beneath. 6 mm. is usually enough. Avoid flooring with a thin surface veneer and especially avoid ‘wood effect’ flooring with a melamine surface stuck to particle board. The thin veneers will be worn through in no time and then the whole floor needs replacing.
  • ceramic tiles may suffer cracks due to hard items being dropped on them so it pays to have a few spare tiles in reserve as it is may be very difficult to match up replacement tiles later.

Types of floor finish

Timber flooring

Techniques in wood flooring have advanced considerably over the last decade or so, especially with the introduction of engineered wood flooring. Jonathan Sapir of Wood and Beyond has contributed a useful article explaining the relative merits of solid and engineered timber flooring finishes and the various grades of timber involved.

Softwood floorboarding

New softwood boarding can provide a beautiful finish providing the following points are covered –

  • the boards must be dried to the correct moisture content (10% – 12%)
  • they have to be properly cramped as they are laid
  • they should be secret nailed

Nearly all the new softwood used in the UK is sourced from Scandinavian 5ths grade or Russian 4ths grade and therefore has a significant way to travel. UK grown softwood is not generally of a high enough quality for the purpose although if you have contacts in the timber or joinery trade you may find that you can source local softwood which is up to quality and have it sawn, dried and machined into floorboards. Particularly attractive can be larch, Douglas fir, pitch pine and yellow pine (though the two latter are almost exclusively from reclaimed material and can be rather expensive).

Hardwood floorboarding

Using native hardwoods for floor boarding can be a very sustainable option because very efficient use can be made of relatively short pieces of timber. Although the common species such as oak, ash and beech are what you normally find in the timber merchants there is also the option to get your own made, especially if you have contacts in the trade. This involves contacting a saw mill and selecting timber, getting it sawn and kiln dried and then finding a company who will put it through a 4 cutter to form the boards. (or you can do it all yourself) This way you will have access to a far wider range of timber species. Alternately you can use reclaimed timber such as that produced by Pine Supplies.

Probably one of the best species for flooring is ash which makes for a very hard wearing surface. It grows plentifully and quite fast in the UK and, being of a honey colour, gives good reflectivity of light. Native ash normally includes the brown heartwood in a small proportion whereas the very uniform light ash is usually imported from the US.

Bamboo is becoming popular as a flooring and is excellent in sustainability terms though the transport involved is a disadvantage.

Penrose tiles

Penrose rhombus floor tiling made from short pieces of oak about 8mm thick

Wood strip, block and parquet

A very economic and easy to lay hardwood floor can be made from timber strips or blocks glued directly to a sub-floor such as 19mm OSB or FSC ply. This works well if you have access to short lengths of timber which are kiln dried (joiners workshops often throw out quantities of standard sized offcuts). Preferably they should be of even thickness and they will need their width regularizing. The lengths can be random. They glue down quickly and easily using remarkably small amounts of foaming polyurethane adhesive. They need sanding finally. This method has the advantage of providing a good floor to work off before the final surface goes down.

Improving old wooden floors

There are numerous DIY web sites which cover this topic but there are a few basic points which cannot be overstated –

  • When levelling up uneven timber floors to take parquet or tiles, at least 15 mm of a good grade of plywood (say pine BCX or better still birch ply) should be laid over the old floor and close nailed or screwed (every 150mm) along the joints. With anything thinner the unevenness will soon show through and damage the top layer.
  • Sanding wooden floor boards has two golden rules; knock all nail heads down slightly lower than the surface of the boards to avoid damaging belts and always try to sand in the same direction as the grain of the wood. Cross grain sanding shows up horribly as soon as you varnish!
Ceramic tiles

Ceramic tiles can create beautiful, resilient floor finishes which are easy to maintain.They are ideally suited for underfloor heating because of their high conductivity and in use they are almost totally inert, giving off no VOCs. The embodied energy is potentially quite problematic and this is to do with how far the tiles have travelled and how difficult they are to replace in case of breakage (see Low maintenance design ). At one end of the spectrum are locally produced quarry tiles and at the other are exotic imported tiles. can be quite low (say 225 MJ/m² – assuming that tiles of 10mm thickness weigh about 25 Kg/m² and embodied energy is 9 KJ/m³).


Cork is an excellent floor finish provided it is laid on a good substrate and well sealed. Its green credentials are excellent due to the way it is harvested and the low amount of energy required to transport it because of its low volume and weight.

Damaged tiles can be sanded back or replaced.

The substrate should be a stable and smooth. You can use a screed or a board such as OSB, plywood or MDF. If it is not tongued and grooved it should be laid with the edge joints perfectly level to avoid them showing through.

Cork tiles can be used in conjunction with underfloor heating but their thickness should be limited to 6mm. as they are a good insulator. Because of the good insulation characteristics and cork being warm to the touch they can be used on uninsulated floors to provide some degree of thermal comfort underfoot.

To a limited extent it will deaden the effect of impact noise.

It comes in a wide variety of finishes and appearances depending mainly on how the cork is cut, the size of crumb and added stains.


The purpose of laminating floor surfaces is to avoid the movement associated with timber. This has become an increasing problem with the growing popularity of underfloor heating which dries out natural timber and causes shrinkage. By cross laminating several layers of timber, a bit like plywood, with the top layer being the visible wearing layer it is possible to stabilise the sheets of material.

However the term laminates covers a multitude of sins with some of the ones which have thinner top layers being hardly worth bothering with. One of the major advantages of timber floors is the ability to sand out damaged areas and this is not possible if the top layer is less than about 3mm. thick to start with, for fear of sanding right through into the layer below. (see Low maintenance design )

Laminate floors can have all sorts of finishes such as bamboo and hardwood parquet patterns. Although quite popular because of their low price, the wood effect melamine faced laminate floors are hardly in the ‘green’ category. They soon show wear in areas of high traffic and there is no way of repairing them – the whole room needs reflooring. (Laminates with a higher wear resistance are available. These are mainly aimed at the commercial market such as shops. The resistance to wear is given in the ‘Taber’ rating)

New on the scene is Baubuche flooring, a LVL material formed from laminates of European beech.


Linoleum is made from pine rosin, linseed oil, saw dust, cork dust, limestone powder, and jute (as a backing). These are all natural materials. Good linoleum can be very attractive and hard wearing. The cheaper end can be awful.


Terrazzo can be used as a finish to a concrete floor. It is in fact simply a screed which is ground and polished to reveal decorative aggregate which is added to the mortar. It is extremely enduring although repairs can be difficult to match with surrounding areas. The cement based terrazzo is generally of much lower embodied energy (and less polluting) than the epoxy type or the polyacrylate type even though the cement type needs to be about 60mm thick compared with only about 10mm for the two plastic types. Premfloor have quite a good description of the processes involved.

Polished concrete

This is similar to terrazzo but with less emphasis on the decorative aggregate (although the aggregate in the concrete can still be chosen for its visual qualities). Concrete can be polished to give an excellent floor finish. It is ground level and then polished using diamond coated disk polishers. This is very slow arduous work and therefore expensive. There are three main ways this might apply

  • on an in-situ concrete slab
  • on a concrete screed (but needs careful design to limit cracking)
  • using concrete floor tiles

In the case of an in situ slab there is a considerable net saving of material while the two other cases simply add more concrete – usually an extra 40mm of it so the embodied energy begins to add up. This is specialized work and needs planning with a specialist sub-contractor. There is an excellent discussion on the Green Building Forum

PVC floor covering

There are several problems with PVC floor tiles, mainly concerning disposal. PVC is very difficult to reuse and incineration is not an option because of dioxin release. PVC will contain approx. 25% phthalates as plasticisers which are implicated with hormone disruption and may also be a carcinogen. Because PVC floor coverings are normally glued to the floor surface beneath they are extremely difficult to remove and frequently the substrate gets destroyed when tiles are lifted

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