The Ontario Building Code | Walls in Public Corridors
9.10.17.5. walls in Public corridors
(1) At least 90% of the total wall surface in any unsprinklered public corridor shall have a surface flame-spread ratingof not more than 75, or at least 90% of the upper half of such walls shall have a surface flame-spread rating of not more than 25.
In Plain Language
For unsprinklered public corridors, this clause caps how flammable wall surfaces can be: at least 90% of total wall area must have a flame-spread rating of 75 or less, or alternatively at least 90% of the upper half of the wall must meet a stricter rating of 25 or less.
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.