Structures are supported by foundations, which transfer their load to layers of soil or rock with appropriate bearing capacity and suitable settling characteristics. They can be used to aid avoid structural settling and other movements, as well as to allow construction on the ground that would otherwise have insufficient bearing capacity.
Pad foundations are typically shallow, but can be deep depending on ground conditions. They are a type of distributed foundation composed of rectangular, square, or occasionally circular concrete ‘pads’ that support localized single-point loads such as structural columns, groups of columns, or framed structures. The pad then distributes this load to the bearing layer of earth or rock beneath. Ground beams in Sydney can also be supported by pad foundations.
They are normally constant in thickness, however, the upper face may be sloping or stepped at points. The nature of the applied load and the permissible bearing capacity of the layers below will determine the plan form. Their thickness must be large enough to distribute the load evenly across the plan shape. Except for the smallest structures, they are normally reinforced, with the reinforcing allowing heavier weights to be applied and the creation of shallower pads that need less excavation and use less concrete.
The pad footings installation in Sydney can be used since they do not require much excavation and are generally appropriate where the bearing capacity of the ground is adequate at relatively shallow depths. They can, however, have a broad plan shape and may be ineffective against the differential settlement, uplift forces, or wind forces.