Site search

you can join words with quotes eg. "solar collectors"



Staircase design

A couple of things about stairs – 1. They usually take up more space than you would first imagine. 2. There are some quite complex Building Regulations which determine the dimensions to do with width, risers and goings.

https://upload.wikimedia.org/wikipedia/commons/thumb/c/c5/Parana_pine_truck.jpg/800px-Parana_pine_truck.jpg

Parana pines, much used in staircase construction

In terms of embodied energy the use of timber in staircases is far better than metal. However the timber should be sustainably sourced and be FSC woodmarked. One of the traditionally favourite timbers for the manufacture of staircases has been parana pine (Araucaria angustifolia) from Brazil but this is now critically endangered.      see more on Parana pine

A fair number of timber merchants and joinery manufacturers in the UK are still claiming to be supplying sustainably sourced parana pine staircases. However the scientific literature from groups such as Geographical Paper No.180 by J.V.M. Bittencourt , University of Reading, shows the devastating manner in which parana pine has been over harvested and it is difficult to imagine how any real volume of the timber can be available on a sustainable basis.

It is on the IUCN Red List of Threatened Species as a critically endangered species.

‘Since 2001 there has been an official Brazilian ban on log exports of this species. The Brazilian Government is also promoting several initiatives to protect Araucaria genetic resources’


Although many staircases are now supplied as whole systems which are modified for the particular purpose, there are still many occasions when it may be better to revert to traditional joinery, metalwork or masonry. This is particularly true where repairs, changes or extensions are being made to a house or traditional features require matching. The exception to this is spiral stairs where it usually makes sense to utilise a prefabricated system.

Staircase design

The stairs always seem to take up more space than you first imagined (often around 8% or more of the total floor area when you include the associated landings) so it is good to work out a rough size and configuration at an early stage of designing a house. This is particularly true for the relationship of circulation space between different floors. There are several factors which influence the design of stairs:

• the vertical relationship of the landings the stairs serve     see more

One straight flight
At its simplest this involves a straight flight with a landing area at the top and bottom. This is usually the cheapest type to build and is most economical in terms of floorspace, taking up about 10 m² in total (i.e. both floors). Because the lower and upper landing are so far apart horizontally it may be difficult to fit in with the room layout. This is the layout generally used when the lower landing is in the hall or living room near the front door.

The spaces around, under and above stairs can range from grubby little cupboards to opportunities to display all kinds of beautiful artefacts such as plants, pictures works of art, creative lighting etc. This is more true with open tread and spiral stairs where the spaces are more visible.

Not that there is anything wrong with cupboards under stairs but given the non-rectangular, somewhat sculptural shape of stairs it provides a chance to be creative. With long straight flights it may leave space beneath the stairs for a doorway through to another room or a small space for a desk, stereo etc.


Half landing return.

Because of space configurations there is often a half landing and then a turn of 180°.

This allows the top landing to be vertically above the bottom one which may be useful with some types of room layout, especially for external stairs. It’s more expensive to build and takes up about 14 m² of floor plan. It may also be more difficult to arrive at a good design for the spaces below the stairs so it can look a bit poky.


Dogleg

Alternately a turn of 90° may work and this configuration can be particularly useful if you are wanting to link lower and upper floors where the circulation spaces don’t match easily, for instance if you are linking together two existing adjacent properties. Adjusting where the half landing occurs on the stairs can also be used to make adjustments between irregular floor levels. Takes up 12 m² of floor plan.


• the aesthetic value of the stairs      see more

Stairs can have several aesthetic components:

They can be beautiful in a purely sculptural way, especially regarding the materials they are made of.

They give a different vertical quality to a space, especially when there is some visual connection between the two storeys they serve:

The book ‘A Pattern Language‘ goes into this in one of its patterns called ‘Staircase as a stage’

“A staircase is not just a way of getting from one floor to another. The stair is itself a space, a volume, a part of the building; and unless this space is made to live, it will be a dead spot, and work to disconnect the building and to tear its processes apart”

The point is also made that people often like to sit on stairs and may use stairs to make an ‘entry’ into a room. So the advice goes:

“Place the main stair in a key position, central and visible. Treat the whole staircase as a room (or if it is outside, as a courtyard). Arrange it so that the stair and the room are one, with the stair coming down around one or two walls of the room. Flair out the bottom of the stair with open windows or balustrades and with wide steps so that people coming down the stair become part of the action in the room while they are on the stair, and so that people below will naturally use the stair for seats.”

Stairs on an outside wall can be lit by a tall window: the Victorians often commissioned stained glass work for these. Half landings can incorporate areas to place objects of beauty or window seats. Pattern Language suggests a window affording a Zen view. Landings can be very interesting areas especially if they are part of a gallery which overlooks rooms below or a courtyard.


the cost which can vary enormously     see more

At the cheapest end is the factory made straight flight of timber stairs with closed risers. At the other end is almost anything you can imagine


• the type of construction and materials     see more

The main structure of the house may suggest the type of stairs which seem best suited. For instance a very heavy masonry structure may be able to support cantilevered treads. Open risers are often used on modern houses. Timber houses would seldom use masonry stairs for structural reasons.
Stair treads obviously need to be hard wearing and it is almost as if stairs have been divided into two types historically: ones which were meant to be carpeted and ones which were meant to be left exposed.

The carpeted ones (usually with timber risers) were normally with softwood treads which wear down if not covered.
The exposed ones tend to be mainly hardwood but also stone, concrete, terrazzo, steel (usually with a covering such as cork, rubber, timber etc.).

If you are using timber for the stairs then this is an opportunity to show off some of our beautiful native timbers. Because staircases use a relatively small volume of timber it is possible to splash out and use the best. Most people know of ash and oak but there are several more exotic species in terms of colour and grain. Native cherry has slightly pink streaks with yellow markings. Native yew is very exotic in terms of its rich red/brown grain mixed with cream. The fruit woods are light in colour and elm has a rich and charming grain. Alder can have strong streaks of red if treated with oil.


• the possibility of stair lifts / lifts     see more

With the growing awareness of Lifetime Homes there is a strong case for considering how stair design might relate to lifts and stair lifts, not necessarily for your own use but also as a way of making a house easier to sell in the future or for the use of a disabled relative. With an ageing population, this will become an increasingly important issue.

The section on Disabled Access indicates how lifts might relate to stairs and landings. In the case of stair lifts there is a case for designing stairs so they may take a stair lift at a later date. This involves the width of the stair, structural support for the lift, adequate space on landings and power supply. It may also have a bearing on the design of service ducts


the Building Regulations

The regulations, (mostly Part K), have a lot to say about stairs. The information below is mainly about calculating pitch and tread size but go to part K to see details on other design requirements such as handrails etc.

Below are extracts from the Building Regulations where stairs in houses are termed ‘Private stairs’ (Utility stair is defined as a stair used for escape, access for maintenance, or purposes other than as a usual route for moving between levels on a day-to-day basis).

(the Scottish Regulations are different in many respects and are somewhat better illustrated in the Accredited Construction Details part 4.3)

Steepness of stairs – rise and going

1.2  Measure the rise and going as shown in Diagram 1.1. (For steps with tapered treads, see also

paragraphs 1.25–1.27.)

1.3  In a flight of steps, for all steps use the measurements for rise and going given for the stair
categories in Table 1.1 below. Use any rise between the minimum and maximum with any going
between the minimum and maximum, that complies with the relevant note contained in table 1.1.

Notes:
[1] The maximum pitch for a private stair is 42°.
[2] For dwellings, for external tapered steps and stairs that are part of the building the going of each step should be a minimum of 280mm.
* The normal relationship between the dimensions of the rise and going is: twice the rise plus the going (2R + G) equals between 550mm and 700mm.


For existing buildings the dimensional requirements in Table 1.1 should be followed, unless due to dimensional constraints it is not possible. Any alternative proposal should be agreed with the relevant building control body and included in an access strategy (refer to Approved Document M).

Steps should have level treads. Steps may have open risers, but treads should then overlap each other by at least 16mm. For steps in buildings providing the means of access for disabled people reference should be made to Approved Document M, Access and facilities for disabled people.

All stairs which have open risers and are likely to be used by children under 5 years should be constructed so that a 100mm diameter sphere cannot pass through the open risers.

There is also a big section on ‘Means of warning and escape‘ under part B, Fire Safety, which is to do with how directly and safely you can get from an upper floor down to a ground floor and out of the building. It can determine much of the design and layout of stairs including fire doors and protected stairs.

Below is an on-line calculator to help work out the dimensions of stairs. Note that the variables can all affect each other so you may need to play around a bit. Bear in mind that the calculator works on clear width and does not take into account the extra width taken up by handrails and other guarding such as balusters or glazing.

Straight stair calculator

This live spreadsheet is based on the Building Regulations and works on the assumption that you have a fixed floor to floor dimension (total rise) but you may want to vary the number of steps and their size and the slope. You can input the number of risers you want and their goings and the spreadsheet then checks whether they conform to the Building Regulations. Enter your guestimate values into the green boxes and then the red text comments indicate whether the necessary conditions are met. Other values such as riser height and pitch get calculated. If the conditions are not met you need to try different goings and risers.

Notes:

  1. Stairs are limited to 36 consecutive risers in a flight unless there is a change in direction. See para 1.14 in the Approved documents.
  2. Risers are not allowed to exceed 220mm
  3. It is important to work to 0.1 of a mm.  (or better) because cumulative error on many steps can become significant
  4. The greater the going the shallower the pitch of the stairs. You can’t have a combination of the maximum risers (220) with the minimum goings (also 220). It makes it too steep (over 42 deg). Longer goings make for shallower but longer stairs.
  5. If this result does not fall within 550-700 try adjusting the risers (via the number of risers) and the goings. The formula comes from the Building Regulations.
  6. if this is above 42 degrees then try increasing the going (or increasing the number of risers to make them smaller)
  7. The total length is the horizontal distance from the nosing on the top landing to the position on the lower landing directly below the lowest nosing. See diag. below

Headroom

The 2000mm headroom rule can be reduced under certain circumstances for loft conversions. (see part K , page 7)

These calculations give you results as if there were no nosings on the treads. That is fine because you can simply add nosings to the steps afterwards without altering the basis of the calculations. However doing so can affect two things: both the headroom and the lower landing width will be reduced marginally. The headroom must always be 2000 min. and the width of the landing is determined by the regulations.

Headroom exemption for loft conversion

A headroom of 2m is adequate on the access between levels (see Diagram 2). For loft conversions where there is not enough space to achieve this height, the headroom will be satisfactory if the height measured at the centre of the stair width is 1.9m reducing to 1.8m at the side of the stair as shown in Diagram 3.

The regulations include various other requirements such as lengths of flights, landings and handrails. See Protection from falling, collision and impact – part K  of the Approved documents.

Spiral staircases

Spiral and helical (centreless) stairs are attractive in several ways

  • They can be extremely elegant and visually satisfying. This is partly the spiral shape itself and partly the visual connection which can be created between the two or more floors. They can also introduce an element of novelty. Spiral stairs are quite sculptural and can sometimes intrigue the mind as to exactly what holds them up. They can be an opportunity for creative lighting, especially in the way shadows of the circling steps can be used.
  • Sometimes they will allow stairs to fit into a space which would be difficult for conventional stairs. However it can work the other way because of the greater width of the treads which is usually required by the Building Regulations.

Considerations

There are several constraints to take into account and they involve the slightly complex geometry of spiral stairs:

  • Is there enough space for them to fit in?
  • Will the turn of the stairs allow for the upstairs landing to be in the right place?
  • Will the upstairs landing work when headroom over the stairs is taken into consideration?
  • Are half landings required?
  • If there is a centre pole, how is it supported?
  • If it is centreless then what supports the whole of the stair structure
  • Is fire proofing between storeys an issue?
  • Do you want a factory made kit system or a custom design?

Space requirements

Most of the factory made systems have good on-line information about the dimensions of their various models and you can establish pretty quickly whether there is enough space.

If you are wanting custom made spiral stairs then the Building Regulations are quite complicated and there are some calculations to do. Basically the regulations are there to make them as safe as normal straight stairs in terms of risers, going, headroom, guarding (handrails etc.), numbers of steps in a run, landings and width of treads.

How much turn?

There is a complex relationship between the going, the riser and the width of the stairs and this determines how much the stair turns. It is, for instance, possible to design a narrow spiral staircase to rise by 2.5 metres with only a bit more than half a turn. But the question arises as to whether you are heading in the right direction when you reach the top. If not you may need a large and awkward landing to get facing the right way. If you have wider going (treads) then you will complete more of a circle.

Headroom and landings

The headroom you need over the stairs may eat into the area of the landing above. There are minimum areas stipulated by the regulations.

Half landings

Half landings may be necessary in some cases such as when adjacent floor levels differs by something other than a storey height. This will then involve a specially made half landing which may not work well with a kit stairs.

Support

Each tread needs supporting and fixing at both ends unless it is cantilevered off a centre post. This can be done a number of ways.

If there is a centre pole it can support the centre end of the treads but it also needs fixing top and bottom. Usually the bottom of the pole has a plate which is fixed directly to the floor. The top of the pole can go up to the floor above (or a structural element incorporated in the ceiling) or it can be fixed to the upper floor, in which case it needs a lateral support which may also serve as the upper landing. This is the most usual configuration.

The outer ends of the treads are often fixed to each other using the ballustrading which supports the handrail. This gives added strength and rigidity to the whole structure.

If the stairs are centreless then there are basically three ways  to support the treads

  • a support wall under the tread ends
  • a structural curved string to both sides of the steps, rigidly fixed at the top and bottom
  • a method of rigidly fixing succeeding treads to each other at both ends so that they effectively form a string similar to stairs with a centre pole.

It may be possible to support the outer ends of treads on surrounding walls either by fixing to them or cantilevering out from them. If they are cantilevered then the stairs can be centreless or there can be a pole, or the steps can be stacked on top of each other.

The Building regs on spiral stairs

The Building Regulations for straight steps generally apply to spiral stairs but there are special methods for measuring curved stairs and design is based on BS 5395-2:1984.

BS 5395-2:1984 is a short document which costs £116 from BSI. Alternately you can view it for free at many of our larger municipal libraries and there are extracts from it on line if you search. The BWF publish an excellent Design Guide: Timber Stairs

For steps with tapered treads the going should be measured as follows:

  • if the width of flight is narrower than 1 m measure in the middle
  • if the width of flight is 1 m or wider measure 270mm from each side

The going of tapered treads should measure at least 50mm at the narrow end.

Where consecutive tapered treads are used a uniform going should be maintained.

Where a stair consists of straight and tapered treads the going of the tapered treads should not be less than the going of the straight flight – these treads should satisfy paragraphs 1.1 to 1.5.

Spiral stair calculator (narrow)

This calculator is based on Approved Document Part K 2010 which in turn uses BS 5395-2:1984

Enter your guestimate values into the green boxes and then the red text comments indicate whether the necessary conditions are met. Other values such as riser height and pitch get calculated. If the conditions are not met you need to try different goings, etc.

Bear in mind that the calculator works on clear width and does not take into account the extra width taken up by handrails and other guarding such as balusters or glazing

The radius is the radius of the outer (larger) curve on the stair. The width is the width of the treads.

Notes for above calculator

  1. Having more risers than the minimum may make for a less steep stairs. The risers will be smaller and the formula (2x riser + going) will allow for longer goings
  2. Controlling by the radius helps to fit the stair within a limited space whereas controlling by the amount of turn may be more important so that the landings are positioned correctly
  3. Adjusting the width affects where the centre line of the steps is and hence the pitch. Note that there is no minimum set width except that means of escape from fire and disabled access should both be considered. Bear in mind that the going on steps is measured to the edge of the nosing (see diagram 1 in section 1 of the Approved Documents part K)
  4. Adjusting the goings affects the pitch and the overall length of the stairs
  5. The formula (2x riser + going) is included in the building regulations and is intended to make for a comfortable and safe stride
  6. The pitch is measured along the centre line of the nosings
  7. If the width at the narrow end is too low you may be able to adjust this by increasing the radius of the stair, having longer goings or setting a lower stair width
  8. The total angle turned will affect the position of landings and which way you are facing when you reach the top (or bottom) of a flight. You may be able to make adjustments by having an extra piece of triangular landing to create the necessary amount of turn
  9. The 2000mm headroom is measured above the pitch line. It can be reduced slightly for certain loft conversion configurations
  10. Bear in mind that after you have calculated the stairs you will need to allow something extra in width for things like the thickness of handrails (and space for hand movement), balustrades, stair construction etc.

Spiral stair calculator (wide)

This calculator is based on Approved Document Part K 2010 which in turn uses BS 5395-2:1984

Enter your guestimate values into the green boxes and then the red text comments indicate whether the necessary conditions are met. Bear in mind that the calculator works on clear width and does not take into account the extra width taken up by handrails and other guarding such as balusters or glazing.

With spiral stairs of a metre or more in width things get quite complicated because the steps have to be checked in two places for steepness and size. (see diag. 8 above) This means there are effectively seven variables which can all affect each other. The best way is to simply play around with the calculator and get a feel of the dynamics. Values such as riser height and pitch also get calculated.

Notes for above calculator

  1. Having more risers than the minimum may make for a less steep stairs. The risers will be smaller and the formula (2x riser + going) will allow for longer goings. Note that with the riser dimension it is necessary to work to fractions of a millimetre since the cumulative effect of many stairs can make a large difference to the overall floor to floor dimension.
  2. Controlling by the radius helps to fit the stair within a limited space whereas controlling by the amount of turn may be more important so that the landings are positioned correctly
  3. Remember that the space needed for the stairs will be slightly larger than the radius because of handrail, banisters etc.
  4. This should be 1000mm or more. If you want it less then use the other calculator above
  5. Increasing the width has the effect of creating a larger difference between the two goings which get measured and this can cause the outer (2R+G) formula to exceed its limit.
  6. Adjusting the goings affects the pitch and the overall length of the stairs
  7. The (2x riser + inner going) formula comes from the Building Regulations and must be satisfied at both going measurement points (270mm in from the end of the steps). The pitch is also measured at both points
  8. The spreadsheet works by first setting the inner size of the step and then checking to see if the outer size is OK
  9. The total angle turned will affect the position of landings and which way you are facing when you reach the top (or bottom) of a flight. You may be able to make adjustments by having an extra piece of triangular landing to create the necessary amount of turn
  10. The 2000mm headroom is measured above the pitch line. It can be reduced slightly for certain loft conversion configurations
  11. The amount of turn may be a more important factor than the space available. If so use this part of the calculator (after first using the very top part where you input the floor to floor height and number of steps)
  12. Increasing the width has the effect of creating a larger difference between the two goings which get measured and this can cause the outer (2R+G) formula to exceed its limit.

Note that the radius of the stairs might be much greater than the stair width.

10 comments to Staircase design

  • bobthebuilder

    Thanks Gideon, British Standards tend to disappear pretty quickly when they are made freely available on the net.

    You have to spend the best part of £100 to buy this one.

    This all goes back to the Thatcher years when “there is no such thing as society” meant that agencies such as British Standards got privatised. This was theft of public information into the private realm.

    But what do you expect from that type of government.

  • Gideon viljoen

    Hi – this is brilliant. THANKS!

    Your link to the BS5395 doc doesnt work though..

    Best
    Gideon

  • M Hopper

    A straight staircase against right hand wall (going up)ground floor to first floor (1970s house)eight feet floor to ceiling, 14 steps, need to know minimum height from front of step to ceiling.

  • Vivienne Mitchell

    Has anybody got any information on who can come and build me a helical staircase or two, preferably good and cheap. Lincolnshire area. many thanks.

  • Fadi

    Hi,
    Thank you for your post. I am designing a helical staircase for a university project, it is composed of 3 parts that get steeper. The risers are respectively 90mm, 105mm, 129 mm. Unfortunatly, if I refer to Part K, the minimum rise should be 150mm. Des this vary BS 5395-2 ? Is there a minimum rise value at all for helical staircases?

    Thank you

  • bobthebuilder

    Hi Carl,

    Not quite sure what you mean by deviation.
    The maximum rise for steps is 220mm and minimum going is 220mm
    But if you mean ‘can you stretch the rules a bit’ then the answer is maybe. You can sometimes get what is called a ‘relexation’ of the building regulations. A relaxation is most often given when changes are being made to existing buildings when a slight ‘bending’ of the rules might lead to some other major gain. E.g. headroom is sometimes relaxed.

  • carl jenkins

    Is there a maximum permissible deviation for the dimensions of each tread / riser?

  • Graeme

    Hi, iwould like to find out about the requirements for supporting a double winder newel post fir stairs leasing to loft, by suspending from a structure above? Supporting from below places the newel right in the middle of the existing srairs. any advice on this approach? Thanks

  • Stephanie

    Thank you so much for this spreadsheet!

  • Mike Earley

    The stair spreadsheet was just want I needed. Everything is included. Perfect – thank you

Leave a Reply

You can use these HTML tags

<a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>

  

  

What is 4 + 3 ?
Please leave these two fields as-is:
IMPORTANT! To be able to proceed, you need to solve the simple calculation above. (so we know that you are a human) :-)