22. Service stairs: Any service stairs shall:
(1) have a minimum width of 550 mm for stairways built or modified on or after 2 August 2001;
(2) have a slope between at least 20° and at most 50° with the horizontal, except for stairways installed before 1 January 1973 which may have a slope up to 60°;
(3) be provided with guardrails along any free side;
(4) be provided with steps having:
(a) a uniform depth and width in any one flight;
(b) a depth of at least 150 mm (nose excluded);
(c) a maximum height of 240 mm, except for stairs built before 1 January 1973 for which the stair height may reach 280 mm;
(5) have a free space of at least 2 m above each stair, measured from the nose or the forward part of the stair.
The depth of stairs on circular or spiral service stairs shall measure 230 mm from the post or the supports for the inside railing.
Subparagraph 5 of the first paragraph applies only to stairs built, installed or modified on or after 2 August 2001 and whose construction, installation or modification does not require a modification of the existing building structure. Stairs that do not have to comply with subparagraph 5 shall have an adequate warning sign.