Methods of damp proofing

Damp proofing is the provision of a barrier or treatment that stops or reduces the entry of moisture from the ground, or from other sources, into a building. The impervious layer used is called a damp proof course (DPC).

General methods

1. Membrane damp proofing (DPC): A continuous impervious layer is put at plinth level (and at other levels) across the full width of the wall. Materials: flexible (bitumen felt, polythene sheet, lead, copper), semi-rigid (mastic asphalt), rigid (cement concrete 1:2:4 40 mm thick, dense bricks, stone slab).
2. Integral damp proofing: Waterproofing compounds (pore fillers such as chalk or talc, or water repellents such as soap, alum, and Pudlo) are mixed into concrete or mortar to make it impervious.
3. Surface treatment: Waterproof plaster, or repellent coatings (silicones, bituminous paint, cement paint), on the wall surface; pointing of joints.
4. Cavity wall construction: An air gap in the wall cuts the path for moisture.
5. Guard (surface) drains and sub-soil drainage: Lower the water table and drain surface water away from walls; an apron round the plinth.
6. Pressure grouting / chemical injection: Cement grout or chemicals injected into the wall to form a barrier in existing buildings.
7. Electro-osmosis: Used for old buildings.
8. Tanking for basements: continuous waterproof membrane on floor and walls.

  Wall
  ======== DPC at 150 mm above ground
  Plinth
  ~~~~~~~~ ground level