What is frost depth in Ontario?
Frost depth is the maximum distance soil freezes downward during winter in a given region; Ontario building codes require foundation footings to extend below this depth to prevent frost heave damage.
Frost depth, also called the frost line, is the deepest point soil freezes during the winter season in your area. In Ontario, frost depth varies by location but typically ranges from 4 to 5 feet below grade. Municipal building departments use these measurements to set minimum footing depths for any permanent structure, including garages.
When soil freezes, it expands, a process called frost heave. If a foundation footing sits above the frost line, ground movement during freeze-thaw cycles can crack concrete, shift the structure, and cause doors or overhead openers to misalign. Building codes enforce frost depth requirements specifically to prevent this damage over time.
Your local municipality determines the frost depth requirement for your property based on regional winter patterns. Before construction begins, builders confirm the exact frost depth standard for your lot, then dig footings deep enough to place concrete footings or posts below that line. This is a non-negotiable step in garage construction and is inspected during the foundation phase.
If you are planning a garage build, your garage builder will pull the frost depth requirement from your municipal building code and ensure all footings meet or exceed it.