The Ontario Building Code | Depth of Foundations
4.2.4.4. Depth of foundations
(1) Except as permitted in Sentence (2), the bearing surface of afoundation shall be below the level of potential damage, including damage resulting from frost action, and the foundation shall be designed to prevent damage resulting from adfreezing and frost jacking.
(2) The bearing surface of a foundationneed not be below the level of potential damage from frost where the foundation,
(a) is designed against frost action, or
(b) overlies material not susceptible to frost action.
In Plain Language
Except in specific permitted cases, a foundation's bearing surface must sit below the level where potential damage (including frost action) could occur, protecting the foundation from seasonal ground movement.
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.