The Ontario Building Code | Maximum Openings
3.1.10.5. Maximum Openings
(1) Openings in a firewall shall conform to the size limits described in Article 3.1.8.6. and the aggregate width of openings shall be not more than 25% of the entire length of the firewall.
In Plain Language
Openings in a firewall follow the same size limits as other fire separations (Article 3.1.8.6) and, in aggregate, cannot exceed 25% of the firewall's total length.
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.