Floating raft is a land-based building foundation that protects it against settlement and

liquefaction In materials science, liquefaction is a process that generates a liquid from a solid or a gas or that generates a non-liquid phase which behaves in accordance with fluid dynamics. It occurs both naturally and artificially. As an example of t ...

of soft soil from seismic activity. It was a necessary innovation in the development of tall buildings in the wet soil of

Chicago (''City in a Garden''); I Will , image_map = , map_caption = Interactive Map of Chicago , coordinates = , coordinates_footnotes = , subdivision_type = List of sovereign states, Count ...

in the 19th century, when it was developed by

John Wellborn Root John Wellborn Root (January 10, 1850 – January 15, 1891) was an American architect who was based in Chicago with Daniel Burnham. He was one of the founders of the Chicago School style. Two of his buildings have been designated a National ...

who came up with the idea of interlacing the concrete slab with steel beams. The earliest precursor to the modern version may be the concrete rafts developed for the building of Millbank Prison in 1815 by Robert Smirke. For a floating raft foundation – or simply "floating foundation" – the foundation has a volume such that, if that volume filled with soil, it would be equal in weight to the total weight of the structure. When the soil is so soft that not even friction piles will support the

building load A building, or edifice, is an enclosed structure with a roof and walls standing more or less permanently in one place, such as a house or factory (although there's also portable buildings). Buildings come in a variety of sizes, shapes, and funct ...

, these types of foundation are the final option and makes the building behave like a boat: obeying Archimedes' principle, buoyed up by the weight of the earth displaced in creating the foundation.

See also