Damp proofing course (DPC) consists of impenetrable material that forms the wall basis preventing any water/moisture from invading the building and causing rising damp. Professional damp proofing specialists are trained to use these materials properly.
The following are some of the materials used.
(A) Flexible Materials – These are materials that are pliable and do not crack or deform when under standard pressure.
- Bitumen Mastic (Mastic Asphalt): Consisting of asphalt or bitumen mixed with fine sand heated up to a spreadable consistency. Carefully, lay with thickness requirement of 2.5 to 5cm. This sets and forms a protective layer.
- Bitumen felts (Sheets): Available in roles of 6mm (thickness) sheets.
- Hotly laid Bitumen: Used on a base of cement or mortar. Preferably apply in two layers of 1.75kg/m2 of the area.
- Metal sheets: Copper, Aluminium or Lead must be used to stop dampness. These sheets are to be used throughout a wall. Only sheets of Lead may be used over Lime Mortar, not
- Cement. Lead causes a chemical reaction. Sheets should be coated with asphalt no less than 3mm.
(B) Rigid Materials – Not resistant to transverse cracks, stresses and severe loading.
- Rich Concrete: For the horizontal DPC a thick layer of Rich Concrete (1:2:4) painted with two coats of hot bitumen may be used where there is no excessive damp. This also stops moisture, by capillary action.
- Mortar: Vertical DPC a 2cm thick layer of Rich Cement with Sand Mortar (1:3) must be applied to the inside of the external walls. Two coats of hot Bitumen must be applied.
- Bricks: Rejected or over cooked bricks, one or two layers may be used for a cheap and efficient DPC. These may be laid in Rich Cement and Sand Stone Mortar (1:3). Bricks are rarely used in DPC, only for cheap housing.
- Stones or Slates: Using 2 layers of stone or slate, laid in Lime, Cement and Sand Mortar makes a good DPC. Otherwise, in Cement Sand Mortar. Generally used when good quality stone is easily and cheaply available.