A damp proof course (DPC) is a barrier installed to stop movement of water by capillary action up through walls and floors. It is also now often referred to as a capillary break. Without a damp proof barrier, moisture moving up from the ground into a home—called rising damp—can cause mold, wood rot, and high humidity in a home. The problem of water moving upward through porous construction materials like masonry, concrete, and stucco, is not new. The Public Health Act of 1875 made DPCs mandatory for all new houses in Great Britain’s year-round damp environment. 

    Early damp proof courses were laid between masonry courses near the ground and were typically asphalt-impregnated or lead sheets, or slate, any of which provided the necessary water resistant barrier. Today there are also metal, plastic, and chemical barriers. Polyethylene sheeting, commonly referred to by the brand name Visqueen, is also commonly used under concrete foundations and floors. It’s also referred to as a vapor barrier and a concrete slab without one can sweat and get slippery after a heavy rainstorm.

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Here’s links to some of our other articles about moisture intrusion problems:

• Why do new homes have more moisture and mold problems than older houses?

• What is a water trap at the exterior walls of a house?

• Where are the most common places to find wood rot on a house?

• How much ventilation is required for the under-floor crawl space of a home? 

 • Why is stucco that goes into the ground a problem at a wood frame house?

• What are the signs of stucco wall leaks? 

• How is water getting into the outside walls of my home? 

• Is mold contagious? Can mold spread to my home if there is a nearby house with mold? 

• What is the right humidity level in a mobile home?

• Why is there mold around the air conditioning vents? 

• What can I do to prevent mold problems in my home?