A basement footer is a concrete block underneath your basement walls that distributes the weight of your home across the surface of the soil. The size of the footer depends on the height of your home, the weight of the materials used to build it and the structural properties of the soil underneath your home.
The size of the footer that a home needs varies according to the ability of the soil to bear weight. The load-bearing capacity of soil is measured in pounds per square foot. Soils that can hold more weight per square foot can support a smaller footer. In order to reduce the amount of shifting in foundations, footers are installed to a depth of 6 inches below the soil's frost line. This limits in the amount of shifting in your foundation when soil freezes, causing it to expand and contract.
The weight of your home and how it is distributed directly affects the size of the footer. Increasing the area of your home does not require a larger footer, however homes with multiple stories increase the amount of weight placed on the footer relative to its total area. Homes that are made with wood framing are generally lighter and can use a smaller footer. If your home uses brick siding or concrete masonry instead it will require a wider footer to accommodate the weight of the home.
The required size for the footer varies dramatically depending on the quality of the soil. In single-story homes the required size of the footer ranges between 6 and 16 inches in homes with wooden framing. In homes with brick veneer walls or hollow concrete masonry a single story home requires a footer between 7 and 19 inches wide. Homes built with solid masonry typically require a footer measuring 9 to 22 inches in width. Each additional story of the home requires an extra 1 to 4 inches of footer width.
The durability of your footer partially depends on how thick it is relative to its width. If your footer is not thick enough relative to its width, it can become damaged over time. As the soil under your home swells and contracts it will cause the sides of your footer extending beyond the wall to bend and crack if it is not thick enough. Homes that have a footer protruding beyond the edges of the basement walls more than 6 inches should have a footer that is at least equal in thickness to the distance from the side of the basement wall to the edge of the footer.
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