Footing in Construction – Classifications and Applications
Footing holds a significant role in the foundation construction. Concrete with rebar reinforcement fills in an excavated structure that forms the footing construction. The main purpose of such construction is transmitting the load of the structure to the underlying soil.
There are generally five types of footings constructed to meet different requirements. Which one should be applied depends on a few important factors like – soil condition, type of super structure and the bearing strata of the structure. The five types of construction are mentioned below:
• Isolated footing
• Combined footing
• Strap footing
• Mat or Raft footing
• Pile footing
Isolated footing: The name says a lot about the construction as the footings are isolated from each other. It supports loads of one column. They are square, rectangular or circular in shape. Such footing construction is applicable where columns are placed at a distance.
Combined footing: This structure bears the load of two or more columns. They are constructed in rectangular or trapezoidal in shape. This footing is needed when isolated construction overlaps. Low soil bearing is also one of the main reasons of getting this combined footing placed.
Strap Footing: It is a type of combined footing where two isolated columns are connected by a strap beam. Such footings transfer the loads from outer column to the inner one, creating bending movement and share force in strap beams.
Mat foundation: This footing construction is placed where the underlying soil has low bearing capacity to withstand the heavy column loads. Such footing construction is required for the large space where other types of footing seem costly.
Pile footing: It is required for low bearing soil to get the maximum support for the structure. Piles come in vertical structure that are drilled into the ground for getting the needed withstand capacity from the deeper soil layer. The foundation is laid on piles that stay separate or in cluster under the soil. The load of the foundation is transmitted to the deeper soil by these piles.