types of footing

2. Group 7
Group Members
Umar Khatab 2013-BT–CIVIL-36
Abid Javaid 2013-BT–CIVIL-09

4. Footing
The lowest load-bearing part of a building, typically
below ground level is called footing
Types of Footing
There are three main types of foundation
• Strip footing
• Raft/Mat footing
• Isolated/Pad footing

5. Footing

7. Strip Footing
 A continuous strip of
concrete under a
continuous wall carrying
a uniformly distributed
load
 Footing spread is usually
provided

8. Strip Footing
Footing spread (150mm on each side) is usually
provided:
i. To facilitate bricklayer a “working space” for
building the lower courses of walls
ii. To provide “stability” to the load-bearing walls
before it is tie down by floors and roof
iii. To provide “working space” for the hand excavation
operation in deeper trench excavation

10. Wide Strip Footing
 Use in a situation where
the load bearing capacity
of the soil is low
(e.g. soft clay silt, made
ground)
 Site which may be
subjected to “unequal
settlement” (mining
areas), or where the
subsoil is “not uniform”
in character

12. Inverted “T” Beam Strip Footing
Use in a situation where
there is a danger of the
foundation failing as a
beam in the longitudinal
direction

14. Deep Strip Footing
A deep strip footing is a
narrow footing which is
used for normal soil and
normal loads and is made
0.9m deep.

15. Deep Strip Footing
In a deep, narrow trench
 Excavation by hand is
not possible
 Brickwork cannot be
built up from the bottom
 Excavation by
mechanical means is
possible

17. Stepped Strip Footing
A stepped strip foundation
is often used on a sloping
site where the steps allow
the foundation to follow
the slope without too
much excavation, when
compared with excavations
and retaining walls.

18. 2013-BT-CIVIL-09

20. Raft/Mat Footing
Raft footing is a
continuous footing that
supports an entire
structure, such as a floor
also known as
foundation mat.

21. Raft/Mat Footing
Best suited in the following conditions:
 Column loads are extremely heavy, thus requiring
large bases
 Columns are closely spaced in both directions and if
pad footings are used, it would overlap and may
almost cover the whole building area
 Ground bearing capacity is low, such as in
compressible soft natural

22. Types of Raft/Mat Footing
 Solid Slab Raft-flat concrete slabs have uniform
thickness over whole raft area, with pedestals or
without pedestals
 Beam and Slab Raft Footing-beam and slab rafts
are alternatives to the solid slab raft and are used
where poor soils are encountered, have pedestals
 Cellular/Framed Raft Footing-these type of
foundations are used on soft compressible subsoil such
as soft clay or pit.

24. Isolated/Pad Footing
Pad footing is the
support used at a point
load such as columns or
framed structures. They
may be circular, square
or rectangular and
consist of a block or slab
of the thickness.

25. Isolated/Pad Footing
 The pad footing may be stepped if they are required to
spread the load from a heavy column. The pads are
usually shallow but deep ones can be found depending
on the structure.
 Isolated or independent slab of concrete foundation to
support concrete columns or steel pillars, detached
brick or masonry piers
 The pier or column bearing on the centre point of the
slab

26. Isolated/Pad Footing
Variation of pad footings:
 Combined Footings – used where the bearing areas
of closely spaced columns overlapped
 Cantilever Footings – designed to accommodate
eccentric loads

27. References
 http://www.ask.com/question/
 http://www.ekt.bme.hu/ArchEng/Foundations%20(S
-D)-s.pdf
 http://en.wikipedia.org/wiki/Foundation_(engineerin
g)
 http://www.architectural-
world.com/2008/04/architectural-presentation-
raft.html