Common types of footings found in structure

The load is transferred to the ground to provide support to the superstructure through the foundation of the building.

Generally, it is the last component of a building to transmit the load into the soil, rock or piles. The main objective of the footing is to expand the loads into the supporting materials so the footing to be designed should not surpass the load capacity of the soil or foundation bed.

The footing compresses the soil and the settlement is created. The amount of settlement is dependent on several factors. Extreme and differential settlement can injure structural and nonstructural components. So, it is necessary to circumvent or minimize differential settlement.

In order to minimize differential settlement, the load of the structure should be transferred consistently. Generally, the footings support vertical loads which should be employed concentrically to get rid of unequal settlement. The depth of the footings should be adequate to attain the necessary soil capacity.

The footings are classified as follow :-

Individual column footing – It is also known as isolated or single footing. It is available as square, rectangular or circular with unvarying thickness.

Wall footing – It is useful for structural or nonstructural walls. This type of footing contains restricted width and a continuous length under the wall.

Combined footing – This type of footing normally support two or three columns not in a row and may be either rectangular or trapezoidal in shape based on column. When a strap connects two isolated footings, the footing is known as cantilever footing.

Mat foundation – Mats stand for large continuous footings, generally arranged under the whole building area to support all columns and walls. Mats are applied for the following reasons :-

1. The bearing strength of the soil is low
2. The loads of the column are heavy
3. Single footings can’t be applied
4. The piles are not applied
5. The differential settlement is minimized through the whole system

Pile footing – Pile footings belong to thick pads which are applied to attach a group of piles together and to support and transfer column loads to the piles.