No matter where you reside, the structure that you live in has a foundation. The foundation is the component of your house that bears the whole weight of the structure and evenly distributes that weight load to the soil or bedrock. The foundations function is essentially to hold the house up by keeping it firmly embedded in the ground, much the same way roots keep a tree standing up straight by gripping the earth. There are several types of foundations commonly found for residential houses.
The first type of foundation is the shallow foundation. Shallow foundations transfer the weight of the structure to the layer of earth very near the surface. Common types of shallow foundations include spread footing foundations, mat slab foundations and slab on grade foundations. Spread footing consists of pads of concrete which transfer weight from the columns and walls to the earth. Mat slab foundations transfer the weight from the columns and walls across the whole building area. Mat slabs are often the material for the basement floor. Slab on grade foundations involve pouring concrete into a mold in the earth and then building a house on top. This form of foundation is more common in warmer climates where freezing and ground thaw are not issues.
The second type of foundation is the deep foundation. Deep foundations distribute the weight of the structure to layers of earth much farther below the surface than shallow foundations. Deep foundations are generally sturdier, and may be employed because of particularly onerous weight burdens, space constraints, or poor surface soil quality. While the terms for the methods used to build a deep foundation vary, the general technique is to drill a column deep into the earth until suitably stable soil is reached. Concrete is then poured into the drilled shaft to provide a stable beam or support for the structure. Another method is to use a pile driver to reach the stable soil. Instead of displacing and upsetting the soil like a drilled shaft, a driven pile will compress the unstable soil around the column and provide greater stability.
Foundations are designed to have adequate load capacity and also to be sufficiently stable in the surrounding soil. Both structural engineers and landscape and geo-technical experts are required to design a truly stable foundational component. Also to be kept in mind for the foundational designer are mitigating factors like scour and frost heave. Scour occurs when water flows over the external soil and removes it from its position of support. Homes with scoured foundations have significant structural instabilities. Frost heave is damage caused by the freezing and thawing of external support soils.
home-inspection
