Hi, does anyone know what the regs are for oversite concrete under a timber floor, we don’t need any sleeper walls to support joist so can we just leave it after taking the soil out, or do we have to stone and concrete it?

  • Rachel Haynes

    Hi, have a look on the Planning Portal website for the Building Regulation Approved Document C – Site preparation and resistance to contaminants and moisture. Pages 25 to 27 has the long winded answer, but in short, in the majority of cases I’m afraid that yes, you will need to stone, DPM and concrete the sub floor. It will greatly reduce the risk of any moisture getting into the construction as well as animals burrowing etc. Also, do check whether you are in a radon risk area and whether any level of radon protection is required.

    If in doubt please do check with the local Building Control.

    Hope that is of use.

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