The Ontario Building Code | Exterior Exit Passageways
9.10.17.4. exterior Exit Passageways
(1) Where an exterior exit passageway provides the only means of egress from the rooms or suitesit serves, the wall and ceiling finishes of that passageway, including the soffit beneath and the guard on the passageway, shall have a surface flame-spread rating of not more than 25, except that up to 10% of the total wall area and 10% of the total ceiling area is permitted to have a surface flame-spread rating of not more than 150.
In Plain Language
Exterior exit passageways have flame-spread requirements set out in this article, addressing this specific type of escape route that runs along the outside of a building.
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.