This document discusses different types of foundations used in construction. It explains that foundations are classified as either shallow or deep, with shallow foundations used for structures up to 10 meters tall and deep foundations like piles used for skyscrapers. Shallow foundations include pad, spread, combined, continuous, and mat foundations. Pad foundations support individual columns, while spread footings distribute a column load over an area of soil. Combined footings support multiple columns. Continuous footings act like cantilevers under walls. Mat foundations provide uniform support under an entire structure. Foundation design considers factors like bearing capacity and preventing differential settlement.

2. FOOTINGS
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Foundation of a structure is like the roots of
a tree without which the tree cannot stand.
The construction of any structure, be it a
residence or a skyscraper; starts with the
laying of foundations.
Foundations are broadly classified into
shallow foundations and deep foundations.
The depth of the foundation means the
difference of level between the ground
surface and the base of the foundation. If
the depth of the foundation is greater than
its width the foundation is classified as a
deep foundation.
Shallow foundations are commonly used in
smaller structures such as residences and
small buildings whose floor height is limited
to 10m whereas Deep Foundations are used
in Skyscrapers…. Piles are the most
commonly used Deep Foundations used in
skyscrapers…

3. SETTLEMENTS OF
FOUNDATIONS
NO SETTLEMENT * TOTAL SETTLEMENT * DIFFERENTIAL SETTLEMENT
Uniform settlement is usually of little consequence in a building, but differential settlement can cause
severe structural damage

4. Bearing Capacity of
Shallow Foundations

5. SHALLOW FOUNDATIONS
• Shallow foundations are those
founded near to the finished
ground surface; generally
where the founding depth (Df)
is less than the width of the
footing and less than 3m.
• Shallows foundations are used
when surface soils are
sufficiently strong and stiff to
support the imposed loads;
they are generally unsuitable
in weak or highly compressible
soils, such as poorlycompacted fill, peat, recent
lacustrine and alluvial
deposits, etc.
Advantages
a)
Cost (affordable)
b)
Construction Procedure
(simple)]
c)
Material (mostly concrete)
d)
Labour (doesn’t need
expertise)

6. TYPES OF SHALLOW
FOUNDATIONS
PAD FOUNDATION
SPREAD FOOTING
 COMBINED FOOTINGS
CONTINOUS FOOTING
MAT FOUNDATION

7. PAD FOUNDATION
Pad foundations are used to support
an individual point load such as that
due to a structural column. They may
be circular, square or reactangular.
They usually consist of a block or slab
of uniform thickness, but they may be
stepped or haunched if they are
required to spread the load from a
heavy column. Pad foundations are
usually shallow, but deep pad
foundations can also be used.

8. SPREAD FOOTING
Footings are designed to resist the
full dead load delivered by the
column. A footing carrying a single
column is called a spread footing,
since its function is to “spread” the
column load laterally to the soil. This
action will reduce the stress intensity
to a value that the soil can safely
carry. Spread footings are sometimes
called single or isolated
footings.
They are square or rectangular pads
which spread a column load over an
area of soil that is large enough to
support the column load. The soil
pressure causes footings to deflect
upward causing tension in two
directions at the bottom. As a result,
reinforcement is placed in both
horizontal directions at the bottom.

9. Footings can be classified according to
their function or shape. The function is
how a footing serves: a spread or
isolated footing (distributes the
column load to an area of soil around
the column), a combined footing
(combines the loads from two or more
columns to the soil), a continuous
footing (one dimensional action,
cantilevering out on each side of the
wall), a pile cap (transmits the column
load to a series of piles which in turn,
transmit the load to a stronger soil
layer at some depth below the
surface), and a strap footing
(transmits the loads from all the
columns to a grid of footings, thereby
bridging weak spots on the surface of
the soil).

10. Rectangular Spread
Footings
Rectangular footings may be used when
there is not enough clearance for a square
footing. In this type of footing, the
reinforcement bars in the short direction
are
placed in the three bands, with closer bar
spacing in the band under the column than
in the two ends. The band under the column
has a width equal to the length of the
short side of the footing, but not less than
the width of the column if that is greater,
and is centered on the column. Under long
narrow columns it should not be less than
the width of the column. The reinforcement
in the band shall be 2/(b+1) times the
total reinforcement in the short direction,
where b is the ratio of the long side of the
footing to the short side. The reinforcement
within each band is distributed evenly, as
is the reinforcement in the long direction.

11. CONTINOUS FOOTING
In this type of foundation the base of
the column is sufficiently enlarged to
act as the individual support. The
widened base not only provides
stability but is useful in distributing
the load on sufficient area of the soil.
Column footings are usually used in
the foundations of residences and
buildings where the soil is hard
enough has has sufficient bearing
capacity.

12. COMBINED FOOTINGS
1. Provides a larger footing to support
two or more columns, and
2. Transfers an eccentric outer
column’s load to a inner footing and
column.

14. MAT FOUNDATIONS

15. Types of Mat Foundation:
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1- Flat plate ---- The mat is of
uniform thickness
2- Flat plate thickened under
columns
3- Beams and slabs
4- Slab with basement walls

16. Slab fabric
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Slab fabric -e.g. previously called
F62 (now SL 62)= fabric 6mm bars
welded together in a 200mm
square grid.
Sheet size 2.4m X 6.0m. Available
in 6, 7, 8, 9, 10, mm diameter bar
sizes (strength of 500 Mpa).
Slab fabric is also available in
rectangular grids. Common sizes
are RL918 (9mm bars at 100mm
centres and 8mm bars at 200
centres) and
RL1018 (10mm bars at 100mm
centres and 8mm bars at 200
centres).

18. THANK YOU !