A damp-proof course is a layer between a foundation and a wall to prevent moisture from rising through the wall. If a concrete floor is laid, it requires a damp-proof membrane, which can be incorporated into the damp-proof course.
Concrete and masonry are both permeable without treatment and, as such, ground water can rise through them by capillary action. This causes a problem called rising damp. Many materials can be used to achieve the impermeable barrier, such as butyl rubber, plastic, lead copper or specially treated bricks. The Romans, 2,000 years ago, used a layer of slate just above ground level in their buildings to prevent rising damp.