Floating raft is type of foundation, invented by John Root, that protects against settlement and the liquification of soft soil due to seismic activity. It was a necessary innovation in the development of tall buildings in the wet soil of Chicago in the 19th century.

For a floating raft foundation, or floating foundation, the foundation has a volume such that were that volume filled with soil, it would be equal in weight to the total weight of the structure.

See also

• Buoyancy
• Building construction