They are much more commonly used in the construction of commercial building in the UK that they are for domestic homes, but can be used very successful in both situations. There are also situations (usually in areas where mining has occurred) where there may be areas of movement in the strata. Rafts are most often used these days when the strata is unstable or (because of this) a normal strip foundation would cover more than 50% of the ground area beneath the building.
#FLOATING FOUNDATION SLAB MAT HOW TO#
Raft Foundations – How to make raft foundations are made When Are Raft Foundations Used This made the entire operation much more difficult and time consuming so raft foundations became less widely used almost overnight. This meant that to use a raft foundation, it had to be designed and approved by Building Control. When the Building Regulations were introduced in 1965 there were no generic rules for raft foundations as there were for strip foundations. The raft foundation was cheaper, easier to install and most importantly, did not require as much excavation as the usual strip foundations. The slab is spread out under the entire building or at least a large part of it which lowers the contact pressure compared to the traditionally used strip or trench footings.īecause of the speed and volume of houses required after the second world war, the raft foundation was widely used.
Raft foundations (sometimes known as Mat Foundations) are a large concrete slab which can support a number of columns and walls.