Foundations consisting of flat reinforced concrete slabs or mats or of reinforced concrete tubs with walls turned up around the edge of the mat to create a larger volume, either designed to move with the surface of the ground without structural damage, or used when the soil is so soft that even friction piles will not support the building load. In the latter case, the floating foundation is used because it makes the building like a boat in obeying Archimedes' principle: it is buoyed up by the weight of the earth displaced in creating the foundation.
