The foundation of most buildings or structures rests on footers or footings. Foundation footings, sometimes called footers, are available in a variety of shapes and designs. Each type of footing is used in different situations and helps to distribute the weight of a structure in different ways. Typically, footings are made of concrete. Soil type and the climate of the region in which you're building will also determine the type of footing used.
Foundation footings, or footers, distribute the load of a structure or building to the soil beneath. This distribution of weight prevents the structure from settling, which can result in foundation cracks and cracks in the walls and drywalls. Sometimes these cracks are harmless, but they may also cause significant structural problems. Footings are typically constructed using reinforced concrete and are usually at least twice the width of the foundation wall. The thickness of the footing used depends on the weight of the structure it is helping to support. For example a thicker footing of about 12 inches will be stronger than one that is 8 inches thick. Footings are installed after excavation of the building site, before the structure is started. The foundation is built on top of the footings, and in most situations the footings are built independently of the foundation. Typically foundation footings are reinforced with steel rebar to improve the footings' overall strength.
The type of footing used in any structure depends largely on the soil condition. In colder climates, footings must be installed beneath the frost line so that they are protected. Shallow or flat-surface footings are used in structures where the soil conditions are ideal and there is no risk of erosion or the soil compacting or shifting under the weight of the structure. Shallow footings are constructed in circular, square or rectangular pads that support a specific load such as a column. Deep foundation footings are often used when the soil is loose and unsuitable to distribute the structure's weight. Piers, for example, are long and shift the load of the foundation through the soil to more suitable materials like rock to provide a solid surface to distribute the load. Piles are also used to carry the load in a similar way, but are used in regions where extreme weather such as high winds affects the foundation's ability to carry the load.
In ideal conditions where soil is firm and compacted, foundation footings are built 6 to 16 inches deep. If the soil is loose, and therefore won't support the weight of the structure, the footings might be built wider and inserted deeper into the ground. In some situations, the soil is removed from the building site completely and replaced with compacted crushed gravel.
Foundations should be placed so that they are centered over the center of the footings, but this isn't always possible. Concrete footings may not be perfectly straight, or must be placed perpendicular to the foundation because of a confined space. As long as the foundation is resting completely on the footings, they can still do their job and distribute the load effectively.
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