The Ontario Building Code | Exception for Exterior Walls
3.1.7.2. Exception for exterior Walls
(1) The limit on the rise of temperature on the unexposed surface of an assembly as required by the tests referred to in Sentence 3.1.7.1.(1) shall not apply to an exterior wall that has a limiting distanceof 1.2 m or more, provided correction is made for radiation from the unexposed surface in accordance with Sentence 3.2.3.1.(9).
In Plain Language
For exterior walls with a limiting distance of 1.2 m or more, this clause waives the usual cap on how much the unexposed surface's temperature can rise during fire testing, provided the design corrects for radiant heat per Sentence 3.2.3.1.(9).
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.