Foundation Requirements

Please refer to us or your builder for full advice on a suitable foundation type, however we enclose some guidelines. Typically a foundation type is decided upon by relevant information such as soil conditions, frost heave, proximity to surrounding vegetation, landscape contour (slope of site), fresh landfill, clay, sandstone, loamy soil, water table and structural load. These are all relevant issues that may affect the foundation type (strip, trench, raft or pad foundation). Excavation in depth and width, concrete thickness and proximity of concrete to finished ground level is also very important in selecting the correct foundation type for your site to save costs within the ground.

foundation

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





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.









Raft foundations


Raft foundations are used to spread the load from a structure over a large area, normally the entire area of the structure. They are used when column loads or other structural loads are close together and individual pad foundations would interact. A raft foundation normally consists of a concrete slab which extends over the entire loaded area. It may be stiffened by ribs or beams incorporated into the foundation. Raft foundations have the advantage of reducing differential settlements as the concrete slab resists differential movements between loading positions. They are often needed on soft or loose soils with low bearing capacity as they can spread the loads over a larger area.