Laying a damp proof course (DPC) is an important part of building. The 1875 Public Health Act first made it mandatory to install a DPC. Building inspectors will check that the cavity wall's two layers are both protected, and ensure that the DPC strips overlap correctly at joins. They also verify that the damp-proof membrane (DPM) on the internal floor extends into the DPC in the walls, creating a seal that prevents moisture from entering. Where else are DPCs used? Damp proof