About this Project

Because the weight of a concrete slab is distributed over many square feet, it usually does not need footings. Slabs "float" (ride up and down) 1 to 2 inches as the ground freezes and thaws. But a footing is required to support a wall of any sort (a dry stone wall is one of the few exceptions). A footing spreads the weight so the wall doesn't sink, so it's usually twice the width of the structure it supports. The footing must extend below the frost line to avoid damage from frost heave. Check local codes to see how deep the footing must be.

To do its job without sinking or shifting, a footing must rest on stable, undisturbed soil. A footing beneath a foundation wall also must have adequate drainage to avoid damage from hydraulic pressure (see Getting to Know Your Structures, Related Projects and Repairing Basement Leaks, Related Projects). To make sure you've planned for the demands of your particular climate and soil conditions, consult with your local building department.