(1) In this section—

“curved stairway” means a stairway, circular in plan, surrounding an open well;

“spiral stairway” means a stairway, circular in plan, which has the treads radiating from, and attacked to, a central column.

(2) Every stairway forming an exit-way or a component of an exit-way, except stairways extending from the ground storey to the first storey of dwelling-houses not exceeding two storeys in height, shall be supported by non-combustible materials:

Provided that combustible material may be used for the finish to risers and treads, to such stairways, other than stairways in basements, if such finish is fixed direct to bases of non-combustible material.

(3) The headroom at every point of any stairway forming an exit-way or part thereof, shall be not less than 2,3 metres, and the width of such stairway shall be not less than the width of exit-ways prescribed by section 26.

(4) No door or window shall open so as to obstruct any stairway forming an exit-way or part thereof.

(5) All treads and risers of interior stairs shall be so dimensioned that the product of the width of tread, exclusive of nosing, and the height of riser, in millimetres, shall be not less than 42 000 and not more than 55 000.

(6) The rise of any step in any interior stairway shall be not more than 200 millimetres, and the width of any tread, measured horizontally between risers, shall be not less than 230 millimetres.

(7) The rise of steps and the width of treads shall not vary by more than 5 millimetres in any one flight of stairs.

(8) Nosings to treads shall project not more than 40 millimetres beyond the face of the riser.

(9) Subject to the provisions of this section, every interior stairway shall be in straight or uniformly curved flights between landings:

Provided stairway, measured from the centre-point of such circle or oral to the nearest point of the tread, shall be not less than 1,8 metres.

(10) No flights of stairs shall have a vertical rise greater than—

a) 2, 135 metres for public and assembly occupancy; or

b) 3,5 metres for all other occupancies;

Without intervening landings.

(11) The length and width of a landing shall be not less than width of the stairway:

Provided that landings on straight flights need not exceed—

Where the stairway is in a building for public and assembly occupancy, 1 metre; or

Where the stairway is in a building designed for single domestic occupancy, 750 millimetres.

(12) Nothing in this section shall prohibit the use of a spiral stairway in any dwelling but such a stairway may only be provided in a building used for a business, commercial or industrial occupancy if –

a) It is additional to the stairway required by sections 23 and 24; and

b) It is not less than 650 millimetres clear in width, no riser exceeds 200 millimetres and the number of treads in a full circle does not exceed 12, or such further number as may be approved by the local authority.

(13) A spiral stairway may be used to give access to a mezzanine floor, where no other means of escape is available:

Provided that –

i) The height of such mezzanine floor does not exceed 2,8 metres above the general floor-level; and

ii) The area of such mezzanine floor does not exceed 100 square metres.

(14) Every interior stairway, except a stairway which is open to the air at every storey-level, in any occupancy-unit falling into any one of classes 1 to 8 in section 4, shall be protected by enclosing-walls constructed of non-combustible materials having a fire-resistance rating of not less than one hour, with doorways fitted with fire-doors having a fire-resistance rating of not less than one hour.

(15) Such doors shall be self-closing, and shall not be fastened in the open position, and such enclosing-walls shall be continuous from the floor of the ground storey to the underside of the roof construction.

(16) Notwithstanding anything to the contrary contained in subsection (14), the following stairways need not be enclosed as therein provided—

a) Any stairway serving a mezzanine storey which has a floor area not exceeding 25 per centum of the floor area of the storey immediately below such mezzanine storey; or

b) Any stairway serving a balcony which has a floor area not exceeding 25 per centum of the floor area of the room served by such balcony; or

c) Any stairway from the ground storey to the first storey, when such stairway is not part of an exit-way.

(17) Every interior stairway shall be provided throughout its length with hand-rails, banisters or railings, in accordance with the following requirements—

a) Every stairway not exceeding 1,1 metres in width shall have at least one hand-rail;

b) Every stairway exceeding 1,1 metres in width shall have hand-rails on both sides of such stairway;

c) Every stairway exceeding 1,65 metres in width in schools and colleges, and all other stairways exceeding 2,2 metres in width, shall have, in addition, intermediate hand-rails dividing such stairways into equal parts not exceeding 1,65 metres wide;

d) Such intermediate hand-rails shall be continuous, be securely supported and fixed without sharp corners;

e) Where any side of such stairway is not bounded by a wall, such side shall be provided with a hand-rail and banisters, or approved railings;

f) All hand-rails shall be fixed at a height of not less than 950 millimetres measured perpendicularly off the intersection of the riser and front of trend, and the height of hand-rails on the landing portions shall be not less than 990 millimetres measured perpendicularly off the landing.

(18) Every exterior stairway forming an exit-way or a component of an exit-way shall be of non-combustible material and be provided with hand-rails, as required by subsection (17).

(19) Each side such stairway which is not protected by a wall shall be provided with a parapet, balustrade, banister or other approved means of protection against falling, having a height of not less than 850 millimetres measured perpendicularly off the intersection of the riser and front tread, or 990 millimetres from the floor of a landing, and such protection shall be constructed of non-combustible materials.

(20) Every such exterior stairway which is not required, in terms of section 26, to exceed 900 millimetres in width, may be constructed of unprotected steel without risers and with treads of not less than 200 millimetres in width:

Provided that –

i) The angle each flight of stairs in such stairway makes with the horizontal shall not exceed 45 degrees; and

ii) The total vertical height of such stairway shall not exceed 18 metres