Spiral Stair Design
- BSI Specifications
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The information below is intended as a guide only and we recommend
that all customers liaise with their local authority Building Control
department or District Surveyor to ascertain the exact requirement for
the individual situation.
The design of all staircases, spiral or otherwise, is governed by Part K of Building Regulations. However, paragraph 1.21 of Part K states that spiral and helical staircases comply with Building Regulations if they are designed to comply with British Standard BS5395 part II (Code of practice for the design of helical and spiral stairs 1984). In essence this means a greater degree of flexibility in design than using the criteria for tapered treads laid down in Part K, particularly with regard to intermediate and floor level landings, inner goings and numbers of risers per flight.
In addition to this, part B (Means of Escape) and M (Access for Disabled) of Building Regulations also apply to spiral stairs in certain situations. External stairways over six metres in height may also require weather protection, such as balustrade panels and canopy roofing.
Below is a summary table of BS 5395 part II giving various categories of stairways.
|
Stair
Category |
Description
|
Min/max
rise per tread |
Min. clear
width between handrails |
Min. going
centre of tread |
|
A
|
A small private stair intended
to be used by a limited number of people who are generally familiar
with stair for example an internal stair in a dwelling serving
one room not being a living room or kitchen, access stair to a
small room or plant in an office, shop, factory, not used by the
public, or fire escape for small number of people.
|
170-220
|
600
|
145
|
|
B
|
A private stair similar to category
A, but also providing the main access to the upper floor of a
private dwelling.
|
170-220
|
800
|
190
|
|
C
|
A small semi-public stair intended
to be used by a limited number of people, some of whom may be
unfamiliar with stair for example a stair in a factory, office,
shop or common stair serving more than one dwelling.
|
170-220
|
800
|
230
|
|
D
|
A semi-public stair intended to
be used by larger numbers of people, some of whom may be unfamiliar
with stair for example a stair in factory, office, shop or common
stair serving more than one dwelling.
|
150-190
|
900
|
250
|
|
E
|
A public stair intended to be
used by large numbers of people at one time for example a stair
in a place of public assembly
|
150-190
|
1000
|
250
|
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