The Ontario Building Code | Noncombustible Construction
3.1.13.8. Noncombustible Construction
(1) In a building required to be of noncombustible construction,
(a) the flame-spread ratings required by Subsection 3.1.5. shall apply in addition to the requirements in this Subsection, and
(b) the flame-spread ratings for exits in this Subsection shall also apply to any surface in the exit that would be exposed by cutting through the material in any direction, except that this requirement does not apply to doors, heavy timber construction in a sprinklered building and fire-retardant treated wood.
In Plain Language
In noncombustible-construction buildings, the flame-spread limits from Subsection 3.1.5 apply on top of these interior-finish rules, and the exit flame-spread limits also apply to any surface exposed by cutting through the material, except for doors, heavy timber in sprinklered buildings, and fire-retardant treated wood.
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.