Choosing the right size
Tilleys London Castings interpretation of Building Regulations relevant to Domestic spiral staircases
Domestic spiral staircases come under 2 aspects of the Building reg’s.
- BS 5395 Part 2 1984.
This states that a spiral serving 1 habitable room should have a 600mm clear width, max rise of 220mm and centre going of more than 145mm.
This would be our 1448mm diameter.
For a main stair serving 2 or more habitable rooms you require a 800mm clear width (900mm in Scotland), max rise of 220mm and a centre going of 190mm.
This would be our 1830mm diameter (2083mm diameter in Scotland).
- Approved Document k.
This states that there is no minimum width requirement but should be built in accordance with BS 5395. I situations where space is limited, the diameter is at the discretion of the building inspector.
It is this clause that allows flexibility with the diameter but we always suggest the client proceeds only with building controls agreement.
All building regulation spirals must comply with the 100mm sphere rule, i.e
there must be no gaps greater than 99mm anywhere on the spiral staircase. So if the client is ordering a Scandinavian, Parisienne or a Victoria 1067 or 1194mm it must have riser bars.
1067mm diameter can have 1 extra Victoria or Plain baluster.
1194mm must have infill (unless 26 degree wooden tread where 1 extra 32mm plain would suffice)
1321, 1448 and 1676mm can have either 2 extra Victoria or plain or infill baluster.
1830 and 2083mm come with 3 Regent balusters but could have Regent Ornate.
Handrail heights.
900mm on spiral staircase and internal balustrade (sometimes when there is a large run of balustrade internally building control will request 1100mm high)
900mm on spiral and 1100mm for external balustrade.
No gaps greater than 99mm.
Loading calculations.(Kilo newtons)
Number of treads x 0.2 + 1.5 for landing plate.
Therefore 12 treads + landing = 12x0.2=2.4 + 1.5 = 3.9Kn
SUMMARY TABLE BS 5395 PART II
CATEGORIES OF STAIRWAYS
STAIRCASE 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 a kitchen, access stair to a small room or plant in an office, shop, factory, not used by the public, or fire escape for a 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 |
|
