A dampproof course is a moisture barrier installed in walls to prevent rising damp and protect buildings from water damage.

A dampproof course (often referred to as a damp proof course or DPC) is a horizontal barrier installed within masonry walls to prevent moisture from rising through capillary action. It is a critical building component designed to protect structural elements and interior finishes from damp-related damage.

In construction, a dampproof course is typically installed near ground level in brick, block, or concrete walls. Common materials include bituminous membranes, polyethylene sheets, metal flashings, slate, or chemical treatments, depending on building type and local code requirements. The DPC creates a continuous break that blocks groundwater from migrating upward into the structure.

From a performance and durability standpoint, an effective dampproof course helps prevent issues such as mold growth, efflorescence, timber decay, and deterioration of finishes. Proper installation height, continuity, and integration with other waterproofing systems are essential to ensure long-term moisture control in both residential and commercial buildings.

Early dampproof courses were often made from layers of slate or lead—some historic buildings still rely on these materials today and continue to perform effectively after centuries of use.

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