9.8.4.1 — Dimensions for Risers

(1) Spiral stairs shall have, (a) handrails on both sides, the outer handrail being not less than 1 070 mm high, (b) a clear width not less than 660 mm between handrails, (c) risers that are not more than 240 mm high, (d) treads that, (i) are a minimum of 190 mm deep at a point 300 mm from the centre line of the inside handrail, (ii) have a consistent angle and uniform dimension, and (iii) turn in the same direction, and (e) a clear height not less than 1 980 mm. (2) Spiral stairs conforming to Sentence (1) are permitted to be used as the only means of egress where they serve not more than 3 persons. (3) Except as permitted by Sentence (2), spiral stairs shall not serve as an exit.