Shallow Foundation

Shallow Foundation are usually located no more than 6ft. below the lowest finished floor. A shallow foundation system generally used when the soil close the ground surface has sufficient bearing capacity, and  underlying weaker strata do not result in undue settlement.  The shallow foundations are commonly used most economical foundation systems. 

The different types of shallow foundation are :

Isolated spread footings:

A spread footing (or isolated or pad) footing is provided to support an individual column. These can be square, rectangular, or circular. Sometimes, it is stepped or hunched to spread the load over a large area.

Wall footings:

A strip footing is provided for a load-bearing wall. A strip footing is also provided for a row of columns which are so closely spaced that their spread footings overlap or nearly touch each other. In such a case, it is more economical to provide a strip footing than to provide a number of spread footings in one line. A strip footing is also known as continuous footing.

Combined footings:

  

Combined footings support two or more columns. These can be rectangular or trapezoidal plan.It is used when the two columns are so close to each other that their individual footings would overlap. A combined footing is also provided when the property line is so close to one column that a spread footing would be eccentrically loaded when kept entirely within the property line.

Cantilever or strap footings:

These are similar to combined footings, except that the footings under columns are built independently, and are joined by strap beam.

Raft or Mat foundation:

This is a large continuous footing supporting all the columns of the structure. This is used when soil conditions are poor but piles are not used.  Mat foundations are useful in reducing the differential settlements on non-homogeneous soils or where there is a large variation in the loads on individual columns.