Above - whacking down the sub base.

The white in the photo above is the 2" thick polystyrene sheets. To the right, the black DPM (Damp Proof Membrane) has been laid over the polystyrene.

Below - the pieces of block used to keep the DPM down until the concrete is poured. The white strips are the tapes used to stick the sheets of DPM together - allow at least 300mm overlap. If the sheets are not stuck sufficiently well then concrete will get underneath and the continuous barrier to water ingress will have been breached

The next photos show preparation for the concrete slab for a garage. Note that, at the front where the garage doors will be, blocks have been left out and temporarily replaced by a scaffold board to retain the poured concrete. This is so that the top of the blocks do not show through when the driveway is completed.