Foundation is a part of structure which interfaces the superstructure to the adjacent zone of soil or rock below it.
The purpose of having a foundation is to transfer the superstructure loads to the underlying soil or rock without overstressing the soil or rock.
Placing the footing at a sufficient depth that the soil beneath the footing is confined. If silt or sand is not confined, it will roll out from the footing perimeter with a loss of density and bearing capacity. Wind and water may erode sand or silt from beneath a footing that is too near the ground surface.
The three basic requirements of a satisfactory foundation.
- The foundation must be properly located with respect to any future influences which could affect its performances.
- The foundation, including the soil below it,must be stable and safe from failure.
- The foundation must not settle sufficiently to damage the structure.
Footing Depth and Spacing
- The frost line
- Zones of high volume change due to moisture fluctuations
- Topsoil or organic material
- Peat and muck
- Unconsolidated material such as abandoned (or closed) garbage dumps and similar filled in areas.