What is the minimum depth for an exterior concrete footing for a structure with an attached unheated garage?

For a structure with an attached unheated garage, the minimum depth for an exterior concrete footing must be below the frost line. This is essential to ensure stability and prevent the footing from heaving or shifting due to freeze-thaw cycles, which can cause significant structural damage.

In colder climates, the frost line indicates how deep the ground freezes during winter months, and footings need to be placed below this line to maintain their integrity throughout the seasons. This depth helps avoid issues related to frost heave, where the expanding frozen ground can lift the foundation and lead to cracks or other structural failures. Therefore, it is critical for the longevity and safety of the structure that the footing is placed below the frost line.