The Ontario Building Code | Exterior Exit Passageway
3.1.13.10. exterior Exit Passageway
(1) The wall and ceiling finishes of an exterior exitpassageway that provides the only means of egressfrom the rooms or suites it serves, including the soffit beneath and the guard on the passageway, shall have a flame-spread rating not more than 25, except that a flame-spread rating not more than 150 is permitted for up to 10% of the total wall area and for up to 10% of the total ceiling area.
In Plain Language
Wall and ceiling finishes (including the soffit and guard) of an exterior exit passageway serving as the sole means of egress are generally capped at a 25 flame-spread rating, though up to 10% of the total wall area and 10% of the total ceiling area may use a 150 rating instead.
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.