Types of Foundations: Design Theory NATA - Architecture - Fashion - Management 2243, Sector 28, Faridabad
Types of Foundations: Design Theory NATA - Architecture - Fashion - Management 2243, Sector 28, Faridabad
Types of Foundations: Design Theory NATA - Architecture - Fashion - Management 2243, Sector 28, Faridabad
Types of Foundations
Before moving into types of foundation, let’s learn what is foundation or footing. Most of the structure consist of two
parts, one above the ground which is known as super structure and the other sub-structure of the foundation which lies
below the ground level. Foundation (aka footing) is defined as that part of the structure that connects and transmits the
load from the structure to the ground soil. The solid ground on which the foundation rests is termed as the foundation
bed. The foundation transmits the load of the structure and it’s self-weight to the soil such that the ultimate bearing
capacity of the soil is not exceeded (the shear failure is not allowable) and the settlement is tolerable.
Every structures are provide with foundation at the base to fulfill the following objectives and purposes:
Foundation are classified on the basis of load transmission to the ground into two sub-categories i.e. shallow foundation
and deep foundation.
Shallow Foundation
Shallow foundation are those foundations in which the depth at which the foundation is placed is less than the width of
the foundation (D < B). Shallow foundations are generally termed as spread footing as they transmit the load of the super
structure laterally into the ground.
Wall Footing
This type of foundation runs continuous along the direction of the wall and helps to transmit the load of the wall into the
ground. Wall footing are suitable where loads to be transmitted are small and are economical in dense sands and gravels.
In this type of foundation the width is 2-3 times the width of the wall at ground level. Wall footing may be constructed
through stone, brick, plain or reinforced cement concrete.
Column Footing
Column footing are suitable and economical for the depth greater than 1.5m. In this type of foundation the base of the
column is enlarged. Column footing is in the form of flat slab and may be constructed through plain or reinforced concrete.
Combined Footing
Combined footings are those foundations that are made common for two or more columns in a row. It is used when the
footing for a column may extend beyond the property line. It is also suitable when the two columns are closely spaced
and the soil on which the structure resist is of low bearing capacity. It may be rectangular or trapezoidal in shape.
Strap Footing
When an edge footing cannot be extended beyond the property line the edge footing is linked up with the other interior
footing by means of a strap beam. Such footings are called as strap footing. It is also know as cantilever footing.
Mat Foundation
A mat foundation is a combined footing which covers the entire area beneath of a structure and supports all the walls and
columns. It is also known as raft foundation. Mat foundation is applicable when:
Deep Foundation
Deep Foundation are those foundations in which the depth of the foundation is greater than its width (D>B). The D/B ratio
is usually 4-5 for deep foundation. Unlike shallow foundation, the deep foundation transmits the load of the
superstructure vertically to the rock strata lying deep. Deep foundations are used when the shallow foundation cannot
support the load of the structure.
Pile Foundation
Pier Foundation
Well (Caissons) Foundation
Pile Foundation
Pile is a slender member with small area of cross-section relative to its length. They can transfer load either by friction or
by bearing. Pile foundation are used when:
The pile foundation can be further classified into following types on various basis such as function, material, method of
installation which are listed below:
Based on Function:
Bearing piles
Friction piles
Combined piles (Both bearing and friction)
Based on Material:
Timber piles
Concrete piles
Steel piles
Pier Foundation
Pier foundation are underground cylindrical structural member that support heavier load of the structure which shallow
foundations cannot resist. Unlike pile foundation, pier foundation can only transfer load by bearing. Pier foundation are
shallower in depth than the pile foundation. Pier foundation are used when:
The term caisson refers to box or a case. These are hollow inside and are usually constructed at the site and sunk in place
into a hard bearing strata. As they are expensive in construction, they are usually restricted to major foundation works.
Well foundation are suitable when the soil contains large boulders obstructing the penetration during installation of pier
or pile foundations. Caissons are used for bridge piers, abutments in rivers and lakes and other shore protection works.
They are used to resist heavy vertical and horizontal loads and are used in the construction of large water front structures
as pump houses.
Shallow foundations are preferred where soil close to the surface is capable of supporting structure loads.
Where the ground close to the surface is not capable of supporting structural loads, hard strata is searched for
and deep foundation is required.
Uniform stable ground requires relatively shallow foundation whereas filled up ground has low bearing capacity
thus requires deep foundation.
In the case of low-rise building in a larger area, the extent of loading is relatively low, so shallow foundation can
resist the load from the structures.
In the case of the high-rise building built within less area have high loads. Therefore, the deep foundation is
required as shallow foundation may not be able to resist such loads of greater intensity.