Pile cap

A similar structure to a pile cap is a "raft", which is a concrete foundation floor resting directly onto soft soil which may be liable to subsidence.

The materials used are long steel bars with longitudinal protrusions between the piles held in shape by thinner tie wires.

Once this steel mat is laid, timber is attached around the perimeter to contain the wet concrete mixture.

Once poured, (usually as a series of small loads), the concrete is stirred to remove any air pockets that might weaken the structure when set.

The concrete undergoes a chemical change as it hardens and this produces a lot of heat.