Shallow foundations are those founded near to the finished ground surface; generally where the founding depth (Df) is less than the width of the footing and less than 3m. These are not strict rules, but merely guidelines: basically, if surface loading or other surface conditions will affect the bearing capacity of a foundation it is 'shallow'. Shallow foundations (sometimes called 'spread footings') include pads ('isolated footings'), strip footings and rafts. Shallows foundations are used when surface soils are sufficiently strong and stiff to support the imposed loads; they are generally unsuitable in weak or highly compressible soils, such as poorly-compacted fill, peat, recent lacustrine and alluvial deposits, etc. Pad foundations
Pad foundations are used to support an individual point load such as that due to a structural column. They may be circular, square or reactangular. They usually consist of a block or slab of uniform thickness, but they may be stepped or haunched if they are required to spread the load from a heavy column. Pad foundations are usually shallow, but deep pad foundations can also be used.
Strip foundations are used to support a line of loads, either due to a load-bearing wall, or if a line of columns need supporting where column positions are so close that individual pad foundations would be inappropriate. The main area of strip foundation are buildings with heavy walls (brick, concrete, stone), and heavy floor slabs. Strip foundation is located on the perimeter exterior walls, and placed under the supporting inner walls of buildings or other areas with increased load. Also strip foundation is well-suited for homes, which is planned to create basement, garage or basement. Strip foundation is also suitable in the case of a possible slight deformation of the base. Typically, strip footing located below the level of soil freezing at 20 cm of sandy soil You can lay the strip foundation and higher...