dampproofing

Damp-proofing is a range of measures applied to buildings to prevent moisture from entering and migrating through walls, floors, and foundations. It aims to control damp caused by rising damp, penetrating damp, or condensation and to protect structural materials, finishes, and occupants from moisture-related damage. It is distinct from waterproofing, which generally seeks to stop active water intrusion.

Dampness in buildings can arise from hydrostatic pressure in the soil, capillary rise in masonry, leaks, poor drainage, or inadequate ventilation. Effective damp-proofing reduces moisture movement to the interior surfaces, limits salt deposition, and helps maintain thermal comfort and indoor air quality. The choice of solution depends on the building type, location, and the extent of moisture.

Common methods include damp-proof courses (DPCs), damp-proof membranes (DPMs), and surface treatments. A DPC is a physical barrier placed at or slightly above ground level in walls to prevent rising damp. DPMs are moisture barriers, often behind finishes or below floors. Chemical damp-proofing uses injectable formulations, applied as creams or liquids that migrate through masonry to create a hydrophobic barrier. Cementitious coatings and bituminous or polymeric coatings can be applied to walls or floors from the interior or exterior. In some cases, internal decorations or plaster are removed to install barriers and restore a dry front.

External damp-proofing is usually preferred for rising damp, while internal treatments may be used when external work is impractical. Proper drainage, ventilation, and roof/plumbing maintenance are essential to prevent recurrent damp, and professional assessment is recommended to select appropriate methods and ensure compatibility with existing materials.