What Is the Minimum Concrete Thickness for an Insulated Raft Foundation?
Why 200mm of concrete? It's the minimum thickness needed to satisfy Building Regulations for fire resistance — not just structure.
When comparing insulated raft foundation systems, one of the first questions architects and engineers ask is about concrete thickness. The answer has implications for structural performance, thermal efficiency, and — most importantly — Building Regulations compliance.
Quick Answer
ISOQUICK designs to a minimum of 200mm of concrete in an insulated raft foundation. This thickness is not driven solely by structural load-bearing requirements — it is primarily specified to satisfy the fire resistance requirements of Building Regulations. A 200mm concrete slab provides the necessary fire protection to satisfy Approved Document B.
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