I am having a 6m x 8m single storey extension built. Because this is near an adjacent slope I have decided as belt and braces to go for piles and ring beam foundation. Building Control are happy with this. The floor is to be the conventional 100mm compacted clean hardcore, blinded with sand, 75 Celotex, DPC, 10mm concrete, 6mm screed. But BC are not happy with this sitting on the ground due, they claim, to differential movement relative to the ring beam system. Anyone else encountered this?