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Ground Stability, Foundations and Substructures 87
Trench or
strip foundation
Pad
foundations
Ground beams – carry
the wall loads to the
pad foundations
(a) Strip foundations – used under
continuous loads such as brick walls
(b) Pad foundations – used under the
point loads of the framed construction
Continuous reinforced
concrete raft foundation
Clusters of pile
foundations
(c) Pile foundations – transfer the load
to lower more stable ground
Figure 3.16 Foundation types.
Ground beams
carry the wall
loads to the pile
Raft foundation –
thickening where point
loads occur
Edge beams may be used to
increase stiffness and rigidity
(d) Raft foundations – spread the load
over greater surface area
Width of foundations
The width of the foundation strip of concrete is determined by the need for room to lay
the walling material below ground level and the requirement for the width of the strip to
be adequate to spread the foundation loads to an area of soil capable of bearing the loads.
The depth or thickness of the strip is determined by the shear strength of the concrete. A
general rule is that the projection of the concrete strip each side of the wall should be no
greater than the thickness of the concrete (see Figure 3.19).