Types of Footing in Building Construction Footing: The function of a footing or a foundation is to transmit the load form the structure to the underlying soil.
The choice of suitable type of footing depends on the depth at which the bearing strata lies, the soil condition and the type of superstructure.
Types of footing
Following are the different types of footing used for concrete structure
1. Isolated footing
2. Combined footings
3. Strap footing
4. Mat or raft foundation
5. Pile foundation
Isolated footings are provided under each column and may be square, rectangular, or circular in plan. Footing may be flat or tapered.
Combined footings are provided to support two or more column loads. These may be continuous with rectangular or trapezoidal in plan as shown. Combined footings become necessary under the following circumstances:
· when the isolated footings overlap.
· when the exterior column is close to the property line with the result symmetrical isolated footing can not be provided.
Strap footing is one of the types of combined types of combined. It consists of an isolated footing of two columns connected by a beam called strap beam. The strap beam does not remain in contact with the soil and thus does not transfer any load to the soil. This is provided when one of the columns is on the property line.
The mat foundation is provided when the soil is having very low bearing capacity and or when columns loads are heavy, the required footing area becomes very large and uneconomical.