The Ontario Building Code | Curved or Spiral Stairs

3.3.1.15. 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 3.4.6.8.(2).