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).
In Plain Language
This clause sets requirements for exit lighting, ensuring exit routes are illuminated to a minimum level so occupants can see well enough to evacuate safely, including under emergency power if normal lighting fails.
This is a plain-language summary of the 2012/2017 Ontario Building Code text above, for general understanding only and not a substitute for the Code. Always confirm current requirements against the 2024 edition (O.Reg. 163/24) or a qualified professional before construction.