Rather than going deep into the ground, Shallow foundation transfers the load of the structure nearer to the surface. This type of foundation is used where digging deep into the ground is not feasible and the structure in not very large. However, the soil on which the foundation is build should have bearing capacity and not be collapsible types. The depth of shallow foundation is less than its width.
Further categorisation based on patter, type of loading and site condition, for Shallow Foundation are:
- Strip Footing:
This footing has maximal length and minimal breadth, as can be deducted from its name, Strip footing. This type of footing is used to support the entire length of a long wall. Also when the spacing between the adjacent columns is very less, strip footing is used as a cost effective alternative.
- Spread Footing:
Spread footing or Isolated footing distribute the load of the column or wall through wider area. It can be either rectangular, circular, stepped or slopped to disperse the load to larger area.
- Combined Footing:
When the distance between two columns is less, such the two separate spread footing will overlay, Combined footing is build. This is done to distribute the load of two columns equally through the footing and also economical. Combined footing could be rectangular or trapezoidal in plan.
- Strap Footing:
Also known as Cantilever footing, it combines two isolated spread footings using a flexible strap of cantilever beam which is not in contact with soil. The rigid strap transfers the load to the soil with equal and uniform soil pressure under the footings of both the columns. It is cost-effective.
- Mat Footing:
This footing covers the entire area, like a floor, with thick reinforced concrete slab like a mat or raft, hence the name. Mat footing is helpful when tolerable soil pressure is low. Also if the adjacent columns and walls are closer, individual spread footing is not possible, then Mat footing is economical.