Definition: a Raft foundation is described as a raft in the sense that the concrete raft is cast on the surface of the ground which supports it, as water does a raft, and the foundation is not fixed by foundations carried down in the subsoil. That is why the raft foundation can be done in many types of soil, like clay, dolomite, or any soil with collapsible potential. It is a solid reinforced concrete structure that support the load of what is built on top of it, with limited deflections or movement in the top structure.
The Raft Foundation firstly needs a proper platform to be constructed in, where we arrange a surveyor for your house/ building to be put out. When a proper platform is in place, we can start with the process of constructing your raft foundation.
The platform is the base where everything starts. We can then do the trenching as indicated on the design of the engineer. Soil poisoning is done before a SABS DPC membrane is used to cover the soil. The DPC membrane helps with waterproofing your foundation, etc. Reinforcing/ steel is fixed and placed in the raft as specified by the engineer. Lastly, the shutters are levelled and checked, spacers are placed between the surface of the raft and the steel, to ensure even cover of concrete. After plumbers and electricians did their job, and the engineer passed the inspection, we can then go ahead and pour concrete. After the raft is completed, it will be 150mm above ground level. It is important to remember to cure the raft for 7 days after concrete was poured to prevent cracks.