Types of Footings in Civil Engineering | What are the different types of footing used in construction

 Types of Footings:

1. Plain footing.

2. Step footing.

3. Isolated/strip/tapered footing.

4. Plain combined footing.

5. Isolated combined Footing.

6. Strap footing or Neighbor footing / shoe footing.

7. Raft footing.

8. Pile footing.

1. Plain footing:

This footing is generally use in house construction where the soil bearing capacity is 24KN/M3. Plain footing is a shallow foundation which is designed to take small loads from column structure without using longitudinal or main bars. This is the most economical form of foundation.

2. Step Footing:

Step footing is defined as a footing which the desired breadth is secured by a series of steps of one unit horizontal dimension to two units of vertical dimension in about the proportion. These types of footings were constructed in olden days, now generally they are not preferred. 

3. Isolated Footing:

These types of footings are constructed for single column and they may be in square or rectangular in shape. It is also known as pad or spread footings. 

4. Combined Footing:

 A footing which has more than one column is called as combined footing. They are build for two or more column and they may be in rectangular or trapezoidal in shape. It is design in a place where the space is limited, where due to lack of space we cannot cast individual footings, therefore footings are combined in to one footing.

5. Strap or Neighbor or Shoe Footing:

Shoe footing is the half footing cut out from the original footing and which has shape of shoe. It is provided on the corner of plot next to Neighbor's plot. Where there is no provision of setback area. They are constructed on property boundary,

6. Raft Footing:

It is one footing in on whole plot and it is provided in a places like seashore area, coastal area or beach area where the water table is very high and the soil bearing capacity is weak. Such as five star hotels and high-rise buildings near the beaches. When number of column in more than one row, provided with a combined footing, the footing is called as Mat or Raft footing.

Process of Executing Raft:

There are two steps involved in executing the raft footing namely.

1. De-watering : It is the process of taking off water from excavated area and discharging it to any other place.

2. Shoring: It is nothing but shuttering for the wall of excavated pit, to avoid the sliding of soil.

7. Pile Footing:

They are constructed where excessive settlement is to be eliminated and where the load is to be transferred through soft soil stratum, where the soil bearing capacity is sufficient. 

- Piles are nothing but round columns, they may be pre-cast or cast in situ.

-  Piles are hammered in to the ground till hard strata layer of earth is found.

- These types of footings are generally designed on sea shore areas.

- These types of footings are provided when the soil bearing capacity of soil is very weak and the 

   ground water table is high.

- The main objective of providing piles under the footing is to prevent structure from settlement.

- If we don't provide pile under the footing, then the building will have settlement.