Foundation Footings Must Be Below the Frost Line

Summary: In areas where the ground freezes a T shaped foundation footing should be used for concrete slab foundations in order to stay below the point where the ground freezes, also called the frost line.

Carl,

I had a basement dug out of sand 70 yards from a small lake. There will be a walk out on the lake side, otherwise back filled to depth.

The entire footing on the non lake side is fully exposed, except for the side sitting on the ground.

The footings were poured in early December. The walls were not poured and the footings are on top of the frozen ground (Michigan winter).

Will there be a problem with them in the spring? What should I look for?

Do they need to be re-done?

I would hate to have the job finished and a problem result.

Thank you, Tim

Hi Tim,

Since you are building in Michigan, footings must be at least 42" below grade in order to be below the frost line.

And, since MI has pretty rigorous building code enforcement, the footings probably are below the frost line. Michigan code requires footing inspections before and after pouring the concrete.

What you are probably (hopefully) looking at is not the footings sitting exposed, but the top of a T-shaped footing.

(Image Courtesy of ConcreteNetwork.com)

This is a method to support a structure in an area where the ground freezes.

A footing is placed below the frost line and then the walls are added on top.

The footing is wider than the wall, providing extra support at the base of the foundation.

First, the T-shaped foundation is placed and allowed to cure; second, the walls are constructed; and finally, the concrete slab is poured between the walls.

For piece of mind, call your building inspection department and ask for a re-inspection.

Carl Heldmann