Building Construction Handbook, Eighth Edition

Summary recommendations of BS 5395-2 ~

Clear headroom ~ measured from the pitch line (consecutive tread
nosings at the geometric stair centre) vertically to any overhead
obstruction. Normally 2.000 m, but acceptable at 1.900 m within
150 mm of the centre column.

Landing ~ Minimum angle subtended at the stair centre is 60°.
Intermediate landings, minimum angle is 45°or a plan area‡ two
treads (take greater area).

Loading guide ~ (No. of treads¾0.2)+(1.5 for the landing)
Eg. 14 treads:
= (14¾0.2)+(1.5) = 4.3 kN.

Refs.
BS 5395-2: Stairs, ladders and walkways. Code of practice for the
design of helical and spiral stairs.
Building Regulations, A.D. K: Protection from falling, collision and
impact.

Stair
type^1

Clear

width^2

Rise Min.

inner

going^3

Max.

outer

going^4

Min.

centre

going^5

(^2) ¾rise

• going

A 600 170†220 120 350 145 480†800

B 800 170†220 120 350 190 480†800

C 800 170†220 150 350 230 480†800

D 900 150†190 150 450 250 480†800

E 1000 150†190 150 450 250 480†800

All dimensions in millimetres.

(^1) See next page.
(^2) Minimum clear width.
(^3) 270 mm horizontally from inner handrail or column face if no
handrail.
(^4) 270 mm horizontally from outer handrail or string (take least
value).
(^5) Centre of clear width.
Spiral Stairs--1