The bottom part of a foundation is called a footing (or footer). The footing is generally wider than the foundation wall and is located about 12 inches below the frost line (the average depth at which soil freezes year after year). The footing distributes the house's weight to prevent future settling or movement.

There are three types of conventional concrete foundations: poured concrete, concrete block and post-and-pier. Size and acceptable types are regulated by building codes. A poured-concrete foundation may be either a raised, perimeter foundation, a flat slab or a combination of the two. Houses in warm climates may have a monolithic slab, where footings, foundation and slab are a single, integral unit.

A conventional perimeter foundation, shown above, has a poured concrete wall supported by a poured concrete footing. Both are strengthened by steel reinforcing rods (sometimes called rebar). This type of foundation is used in connection with both raised floors and slabs.

Foundation Footings

Stepped footing can support a concrete block wall. Blocks have nominal dimensions of 8 by 8 by 16 inches (the actual dimensions are actually 3/8 inch smaller than these to allow for mortar joints). They are hollow when laid-up; steel reinforcing bar called rebar is added and the hollows in the blocks are often filled with concrete. They lend themselves to construction where forming concrete is difficult or impractical.

Concrete blocks are also used for standard foundation wall construction. Here they are supported by a concrete footing; both are reinforced with steel rods and the concrete blocks are filled with grout.

A concrete pier, resting on a footing, may be used to help support beams at mid-span. Though some older homes rest entirely on piers, this method has been phased out in favor of stronger foundations.