The Ontario Building Code | Walls in Exits
9.10.17.3. walls in Exits
(1) Except as provided in Sentence (2), at least 90% of the exposed surfaces of every wall in an exit shall have a surface flame-spread rating of not more than 25.
(2) At least 75% of the wall surface of a lobby used as an exitin Article 9.9.8.5. shall have a surface flame-spread rating of not more than 25.
In Plain Language
Walls in exits have specific flame-spread requirements set out in this article, parallel to the ceiling requirements but applying to the vertical surfaces of the escape route.
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.