The Ontario Building Code | Curved or Spiral Stairs
22.214.171.124. Curved or Spiral Stairs
(1) A curved or spiral stair is permitted in a stairway not required as an exit provided the stair has,
(a) treads with,
(i) a minimum run not less than 150 mm, and
(ii) an average run not less than 200 mm, and
(b) risers in conformance with Sentence 126.96.36.199.(2).