Concrete block size used in a house foundation

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Concrete block size used in a house foundation
Block foundation walls provide durable foundations. (concrete block background image by pcphotos from

Concrete blocks used for foundations in homes measure 8 inches by 8 inches by 16 inches. The true measurements are 7 5/8 inches by 7 5/8 inches by 15 5/8 inches. The true measurements allow for the application of mortar between the blocks to bond them together. Concrete blocks also come in 10-inch lengths, but their use as foundation material is uncommon.

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A building's foundation supports most of the weight of the home and based on the American Society for Testing and Materials (ASTM) standards, each block can support 862 Kilogram per square inch (PSI). The blocks can also form the walls of a basement.


Although each block has a standard length, width and depth, blocks vary in shape depending on the use of the block. Corners require specific blocks and sometimes builders use bullnose or rounded-corner blocks for finishing corners. Blocks also vary by the number of cavities inside them. Blocks with two holes provide more structural support for foundations, while three-hole blocks work well for constructing fencing for a yard.


A concrete block foundation weathers over time quite well, since few conditions exist that can degrade the blocks. After building a concrete foundation, contractors paint the outside of the blocks with tar or similar waterproofing paint so the blocks resist water. Unlike wood, concrete block foundations are impervious to termites and other burrowing insects.

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