Wednesday, March 9, 2011

Building Foundation

To build a house should intend to the foundation structure. A foundation supplies the base for a structure such as a building, bridge, dam, or breakwater, transmitting the load of the superstructure to the supporting soil or rock in such a way as to prevent the setting or slippage of the structure.

The construction of a foundation is preceded by a study of the material on which the structure is to be built, including test pits and boring to determine the type of soil and the depth at which rock or water are encountered.

Foundations tail into two general classifications; spread and deep. A common type of spread foundation is the footing, a slab, block, or pedestal that forms an enlargement of the bottom of an individual pier or bearing wall and distributes the load to the broader area of raft foundation, is used for heavier, more widely distributed loads. It consists of a number of footings combined into a single, thick reinforced concrete slab beneath the entire structure. A third kind of spread foundation, which is used in soil that may settle or slide, is the floating foundation, a boxlike underground construction with a weight equal to or slightly exceeding that of the excavated soil.

There are two principal types of deep foundations, piles and cassons. Piles which can be made of timber, concrete, or steel, are driven by hammers into the ground. End bearing piles are sunk to the bearing stratum (the depth at which soil resistance can support the weight of the structure), or sometimes to bedrock. Friction piles, which are rough surfaced and tapered, transfer their load to the adjacent soil along the length of the pile through friction and adhesion. Caissons are hollow boxlike or cylindrical structure.

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