A damp proof membrane (DPM) or vapour control layer (VCL) is a material used in to protect the floor and the insulation from moisture. The DPM is usually installed on the concrete slab, prior to the insulation layer being installed, thus creating a moisture barrier that prevents rising damp. After installing the insulation layer, a VCL is installed on top before the screed layer is poured to prevent the insulation absorbing moisture from the screed. Warmup provides two types, a 1200 gauge DPM and 500 gauge VCL. The DPM can be used in place of the VCL but not vice versa.