A raft foundation is usually used when building in low soil
bearing conditions; it is used to distribute the building pressure over a large
area so that the soil can bear the stress.
Raft foundations normally consist of reinforced concrete
which extends over the entire loaded area. Can be stiffened by beams or ribs
incorporated into the foundation.
Raft foundation can also be utilized on ground conditions
that do not specifically need a raft because it is much faster to construct.