The Ontario Building Code | Thickness of Exterior Walls
9.20.6.1. Thickness of exterior Walls
(1) masonry exterior walls, other than cavity walls, in 1 storey buildings and the top storeysof 2 and 3 storey buildings shall be not less than 140 mm thick provided the walls are not more than 2.8 m high at the eaves and 4.6 m high at the peaks of gable ends.
(2) The exterior walls of the bottom storeys of 2 storey buildings, and exterior walls of the bottom 2 storeys of 3 storey buildingsshall be not less than 190 mm thick.
(3) In exterior walls composed of more than one wythe, each wythe shall be not less than 90 mm thick.
In Plain Language
Exterior masonry walls must meet minimum thickness requirements set out in this article, appropriate to their structural and weather-exposure role.
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.