The article explains the types of building foundations, i.e., shallow and deep. Further, the examples, uses, design criteria of each of the shallow and deep foundations have been described in detail.

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Civilverse Admin 10 April 2021
Types of Building Foundations-Shallow & Deep
civilverse.org/types-of-building-foundations
Table of Contents for types of building foundations-
1. Introduction
2. Types of building foundations- Shallow & Deep
3. Shallow Foundations
4. Deep Foundations
1. Introduction
The foundation is the bottom-most part of any structure that connects it to the ground.
The foundation transfers the load of the building to the earth. The selection of the type of
foundations depends upon the load of the building, bending moment generated due to it,
uplift pressure of soil, safe bearing capacity of the soil, space constraints etc.
The basic requirement of a foundation of a structure is to distribute the load over an area
to avoid failure. The foundation should be made with durable materials as it is subjected
to corrosive attack by soils, frost, water table changes, swelling and shrinkage of soil etc.
The change in length, width, depth and shape leads to different types of building
foundations that have distinguished behaviour from each other. The foundations are
made after carrying out the excavation works.
2. Types of Building Foundations

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In general, the load-carrying capacity of the soil increases with the increase in depth. The
soil strata become firm with the depth. The foundation type is such selected that it can
transfer the load to the sufficiently hard strata. Thus, the soil having lower strength
require foundations to go deeper. This requirement leads to the classification of
foundations on the basis of their depth.
The foundations are broadly classified two into heads, shallow foundation and deep
foundation.
Criteria to decide the type of building foundation
The foundation that has width to depth ratio lesser than or equal to two is called shallow
foundation.
Similarly, the foundation having width to depth ratio greater than two is called deep
foundation.
Deep foundation generally carries higher loads for the same plan area.
3. Shallow Foundation
A shallow foundation is cheaper to construct as it rests on the soil near to the surface. It
can carry only smaller loads. It is suitable for soils with sufficiently good safe bearing
capacity. The shallow foundations are of the following types-
Types of Shallow Foundation
3.1 Isolated Footing
Isolated footing is an individual footing to a column. It is made where the soil strata are
sufficiently hard and non-expansive. The isolated footing is one of the most common
types of footing made in small scale construction works especially residential buildings.

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Isolated Footing
The isolated footing can be made of following types such as simple rectangular, stepped
and trapezoidal.
The isolated footing is not recommended where the soil settlement is higher.
3.2 Combined Footing
A combined footing is used where the column is spacing is lesser and the individual
footings would foul with each other. It is also an economically feasible option for the
nearby columns. It accommodates more than one column on a single base slab. The
combined footing can be made either rectangular or trapezoidal.
Combined Footing
The combined footing has lesser settlement than the isolated footing.
3.3 Strip Footing

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The strip footing has a greater length than the width of the foundation. This footing is
made under the walls or closely spaced columns. The strip footing can be made of
concrete or masonry. Generally, the stone masonry wall has stone masonry strip footing
and the brick wall has brick masonry strip footing.
Strip Footing
3.4 Strap Footing
When two individual footings are joined together by a rigid beam, it is called strap
footing. The strap footing is an alternative to combined footing when the column spacing
is larger. The strap footing is an economical option.

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Strap Footing
The beam connects the individual footings and makes the structure behave as a single
unit. The beam centreline aligns with the centreline joining the two columns.
3.5 Mat Foundation
When the load is heavy or the column’s individual footings are overlapping, the mat
foundation is made. The mat foundation contains a big slab supporting the columns. The
mat foundation as the name suggests covers the entire built-up area of the building. The
mat foundation is bulky and very expensive as the concrete quantity and excavation are
more.
Mat Foundation
The mat foundation is very much resistive to the differential settlement of the soil.
3.6 Raft Foundation
The raft foundation is an economical version of the mat foundation. The concrete quantity
is lesser than the mat foundation for the same built-up area. The raft foundation is also
useful in resisting the differential settlement of the soil.

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Raft Foundation
The raft foundation is very commonly made for big residential, commercial and industrial
buildings.
4. Deep Foundation
The deep foundation is made to carry heavier loads or where the safe bearing capacity of
soil is lesser than the required value or for both of the reasons. A deep foundation is also
useful in expansive soils. The types of deep foundation are as follows-
Types of Deep Foundation
4.1 Pile Foundation
The piles are vertical slender columns supporting a raft called a pile cap. The pile cap
takes the load of the building and transfers it to the piles. The piles can be precast, cast-in-
situ, driven and drilled.
The mode of load transfer from pile to the earth can be any of the following three types-
i. Friction
ii. End Bearing
iii. Combination of Friction and End Bearing
The piles are very common type of deep foundation used in residential, commercial and
industrial building.

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The piles are circular in cross-section
with having up to 600 mm diameter
and are made of timber, steel or
reinforced concrete etc.
Read more about pile foundation
here.
4.2 Pier Foundation
The piles having a diameter of more than 600 mm are called pier foundation. The pier
foundation can also be of any of the friction pier, end bearing pier or combination of both.
Pier foundation is generally drilled and cast-in-situ.
Pier Foundation
4.3 Basement

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Basement is constructed where space is required below the ground level. They support the
entire building by connecting the base slab and ground-level slab by columns or load-
bearing walls or both.
The basement has walls on the outer periphery that support the lateral earth pressure.
The ability to support vertical loads as well as lateral pressure and space availability make
the basement a desirable foundation type. The basement is often used in residential and
commercial buildings for parking.
Basement Foundation (Image Courtesy-The Spruce)
Basement is constructed in open excavation.
4.4 Well or Caisson Foundation
A well or caisson foundation is made by digging a circular cross-sectional area and sinking
a precast unit into it. The precast unit is made near the site and lowered into the pit.
Caisson Foundation (Image Courtesy-Stock Adobe)

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Caisson foundation has a huge load-carrying capacity. They are generally used in heavy
construction such as bridge construction, oil rigs etc.
4.5 Buoyancy Foundation
The buoyancy foundation is a hollow box type foundation that is designed to decrease the
load intensity on the ground beneath. It is made on silts, soft sands and alluvial deposits.
Buoyant Foundation (Image Courtesy-Researchgate)
The buoyancy foundation is expensive and thus rarely used.
4.6 Cylinder
Cylinder is small sized caisson.
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Read more about excavation here and foundations here.