Damp Proof Course

A damp proof course (DPC) is a physical barrier built into the walls of a property at or near ground level to prevent moisture from rising up through the masonry. Modern DPCs are typically made of a waterproof membrane installed during construction. In older properties without an original DPC, a chemical injection DPC can be inserted.

The DPC sits approximately 150mm above external ground level. One of the most common causes of DPC failure is "bridging" - where soil, paving, render, or other material has been built up against the outside of the wall to a level above the DPC, allowing moisture to bypass the barrier and enter the wall above.

Signs of DPC failure or absence include: rising damp on ground floor walls (dampness that starts at floor level and extends to 1-1.5 metres up the wall), white crystalline salt deposits on walls (efflorescence), tide marks of staining, and musty odour.

Damp problems affect tenantability, EPC ratings, and property values. Treating rising damp requires identifying and removing the bridging source, inserting or repairing the DPC, and replastering with specialist salt-resistant plaster. Costs range from £500-£3,000 depending on extent, and the work must be done correctly to avoid reoccurrence.