I have a concrete slab (say 12'square) which is level with the DPC in the garage and along one wall of the house. I want to lay slabs on top of this and have been told that I can put a DPC under the edge of the slabs and then simply turn it up along the sides! Conversely, I have been told to leave a gap of say 10cms and fill with pea shingle once the slabs are laid. I don't know what is best nor indeed, what is in line with building regs. Can anyone help please.