The materials used for damp proofing are:
1. Bitumen: In hot condition it is highly flexible and can be applied with brush to the bedding of concrete or mortar. Thickness of coat provided is about 3 mm.
2. Mastic asphalt: It is a semirigid material. It is obtained by heating asphalt with sand and mineral fillers. It is perfectly impervious. It should be laid very carefully.
3. Bituminous or asphaltic felt: It is a flexible material which is available in rolls. It is provided on roof slabs and parapet walls with an overlap of 100 mm on sides. The laps are sealed with bitumen. They do not withstand heavy movements.
4. Bricks: Good bricks with water absorption less than 5 per cent are sometimes used to make damp proof courses. The bricks are laid in two to four courses in cement mortar.
5. Stones: Stones like granite, trap and slates may be laid over wall to its full width as damp proof course.
6. Mortar: Cement mortar of proportion 1 : 3 with small quantity of lime and water proofing agents are used to make a water proofing course to foundations, ground floor slabs, top of parapet walls etc. It may be used for plastering external walls.
7. Concrete: To check the rise of water into walls a course of 75 mm to 100 mm cement concrete 1 : 1 1/2 : 3 or 1 : 2 : 4 is provided before starting constructing walls. These courses may be provided with hot bitumen paint as an additional precaution.
8. Metal sheets: Aluminium, copper or lead sheets are provided to seal the construction joints.
Over these sheets bituminous seal is provided.
9. Plastic sheets: Plastic sheets are very good course for damp proofing. They are made up of black polythene of thickness 1 mm.