The building structure is basically of two parts . The structure above the ground which is called as Super Structure and the structure below ground level is called as Sub Structure or the foundation .

This substructure or the foundation transfers the load of the super structure to the ground evenly and keeps the structure stable. The loads are transferred to the ground through footings which are at the base of the columns.

The selection of the suitable foundation depends upon factors like
1) Loads from the structures
2) Type of soil .
3) Type of superstructure
4) Type of adjoining structures.

Lending upon the bearing capacity of the soil and the depth of foundation required, there are two types of foundations that are made.
Shallow foundation and the Deep foundation .
Shallow foundations are footings which support small and light structures. The term Footings are used only for shallow foundations. Broadly shallow foundations are those whose complete process of casting is seen are shallow foundations. They are also known as open footings. These foundations are normally upto 3 meters depth. It can be more in favourable conditions.
Deep foundations are foundations made at greater depths for buildings having larger loads, and the bearing capacity of the soil is less.

Shallow foundations are further divided as follows

1) Continuous or strip footing , they are used for load bearing structures .
2) Isolated or the pad footing
3) Combined footing
4) Eccentric footing
5) Strap Footing
6) Raft Foundation ,

Raft foundations are further divided into
a) Flat plate type
b) Flat Plate thickened under column
c) Flat Plate with Pedestals
d) Two way beam and slab type
e) Cellular Construction
f) Basement Walls as rigid frame.

Deep Foundations are mainly of two types
1) Pile foundations
2) Caisson foundation.

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