Stairs are used to create a pedestrian route between different vertical levels by dividing the height between the levels into manageable steps.
Very generally, the word 'stairs' refers to a staircase, whereas the word 'step' refers to the steps that make up the staircase.
The main components of stairs are illustrated below:
Stairs can be straight and can include a landing and turn, or can be curved. A continuous series of steps between landings is called a flight.
Under some circumstances, stairs can have alternating treads, that is, the wide part of the tread is on alternating sides on consecutive treads.
|Helical stair||Alternating tread stair|
- Approved document K: Protection from falling, collision and impact.
- Approved document M: Access to and use of buildings (only when external stepped access also forms part of the principal entrances and alternative accessible entrances and when they form part of the access route to the building from the boundary of the site and car parking).
- Approved document B: Fire safety.
The very broad requirements are set out in summary below, but for the full detail, you should refer to Approved Document K.
 General requirements
|Min rise (mm)||Max rise (mm)||Min going (mm)||Max going (mm)|
|General access stair||150||170||250||400|
This gives a maximum pitch for a private stair of 42 degrees.
The normal relationship between the rise and the going is that 2 x the rise + the going should be between 550mm and 700mm.
Other requirements include:
- For school buildings, the preferred rise is 150mm and the preferred going 280mm.
- For dwellings, for external tapered stairs that are part of the buildings, the going should be a minimum of 280mm.
- For existing buildings, alternatives may be proposed if the dimensional constraints do not allow these requirements to be followed.
- There are more complex requirements for stepped gangways in assembly buildings, and there may be conflict between these requirements and sight lines in some buildings with spectator seating.
- Buildings that are not dwellings and common areas in buildings that contain flats should not have an open riser, should have visual contrast to make nosings apparent, and nosings should not protrude by more than 25mm.
- The minimum headroom should be 2m.
Buildings other than dwellings
- For stairs that form part of a means of escape, see Fire below.
- For other stairs, a minimum width of 1,200mm, and 1,000mm between handrails. If the stairs are more than 2m wide, then they should be divided into flights of no less than 1,000mm.
- For stairs that form part of a means of escape, see Fire below.
- Where it is necessary to have a stepped change of level within the entrance storey, this should be a minimum width of 900mm.
Landings should be at least the width and length of the minimum width of the fight. For buildings other than dwellings, each landing should have an unobstructed length of at least 1,200m.
NB In designing staircases, in particular residential work, thought must be given to access for furniture. Spiral staircases for instance are a real problem for bedroom furniture and windows may not have big enough openings for alternative access.
 Length of flight
Stairs with more than 36 risers in consecutive flights should have at least one change in direction between flights. For buildings other than dwellings, the maximum number of risers between landings should be 16 for utility stairs and 12 for general access stairs. There should not be any single steps.
Handrails should be 900mm to 1000mm from the pitch line or the floor. If the stair is 1,000mm wide, or more, a handrail should be provided at both sides. If the stairs are more than 2m wide, then they should be divided into flights of no less than 1,000mm.
In buildings that might be used by children under 5, guarding should be designed so that a 100mm sphere cannot pass through, it should prevent children being held fast and should be difficult to climb.
There are specific and complex requirements for the fire separation of stairs in dwellings depending on the height of the building and whether there is a basement. There are also specific requirements for external escape stairs (For details See Approved Document B - Fire Safety: Volume 1 – Dwellinghouses).
In relation to buildings other than dwellings, there are also specific and complex requirements in relation to the number of ‘protected’ stairs, firefighting stairs and the width of stairs. (For details see Approved Document B - Fire Safety: Volume 2 - Buildings other than dwellinghouses).
The main accessibility requirements for stairs have now been moved to Approved Document K, however, there is still guidance in Approved Document M: Access to and Use of Buildings in relation to external stairs, where they also form part of the principal entrances and alternative accessible entrances and when they form part of the access route to the building from the boundary of the site and car parking (For details see Approved Document M: Access to and Use of Buildings).
 Types of stair
An alternating tread stair is a stair with paddle-shaped treads where the wide portion is on alternate sides on consecutive treads.
See: Alternating tread stair for more information.
Approved document B defines a ‘protected stair’ as ‘…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 construction’.
See: Protected stairway for more information.
 Related articles on Designing Buildings Wiki
- Accommodation stair.
- Approved Document K.
- Building regulations.
- Inclusive design.
- Landings in buildings.
- Maximum length of a flight of stairs.
- Newel post.
- Spiral stairs and helical stairs.
- Stairs going.
- Stairs nosing.
- Stairs riser.
- Stairs string.
- Stairs tread.
- Wheelchair platform stairlifts.
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