A damp-proof course (DPC) is a horizontal barrier in a wall designed to resist moisture rising through the structure by capillary action - a phenomenon known as rising damp. DPC is used to stop dampness in buildings. In theory, due to capillary movement of water, water rises from the earth to the building. Passing through the foundation it rises higher to reach the walls. If water reaches the walls it may damage them by creating cracks, breaking cement-paint bonds and creating dark-spots on the wall etc. So, to avoid water from reaching to the walls DPC is laid.