What is Damp Proof Course ?
In order to prevent the entry of damp or moisture in the building, the damp proof course (D.P.C) is provided at various levels of the entry of damp into building. At present, generally all the buildings are given the treatment of damp-proofing. Thus the provision of damp-proof course prevents the entry of moisture from walls, floors and basement of a building.
Causes of Dampness
Dampness in the building is due to one or more of the following reasons mentioned below :
- The faulty and inappropriate design of the structure can be the major cause of the dampness in the building.
- Unskilled labours can lead to poor workmanship which further results in faulty construction.
- Poor materials used for the construction of the building.
- All of the above causes results in rising of moisture from the ground, rain water travels from wall tops if proper water-proofing is not done, condensation, poor drainage, imperfect orientation, imperfect roof slope etc.
Effects of Dampness in Building
- The building suffering from dampness causes unhealthy and difficult living and working conditions for the residents.
- It may result in softening and crumbling of plaster.
- Efflorescence is mainly caused due to dampness which results in the disintegration of tiles, bricks, stones etc and reduces strength of building.
- It may cause bleaching and flaking of the paint which results in the formation of coloured patches on the wall surfaces and ceilings.
- Metals used in the construction of the building may get corroded.
- If wooden (timber) items in the building such as furniture or cupboard get in contact with dampness sections it may get deteriorated.
- Dampness also promotes the growth of termites which is again a bad sign for timber items.
- Electrical fittings can get damaged and it has potential to create short circuit.
Materials Used for Damp Proof Course
- Hot bitumen.
- Mastic asphalt.
- Bituminous or Asphaltic felts.
- Metal sheets.
- Combination of sheets and felts.
- Cement concrete.
- Plastic sheets.
Ideal Characteristics of Damp Proofing Materials.
- They should be perfectly impervious.
- Materials used for damp proofing course should be durable.
- They should be sufficiently strong and capable of resisting superimposed loads coming on it.
- It should be flexible so that it can accommodate the structural movements without any fracture.
- It should remain steady in its position when once applied.
- The material should not be costly and easily available.
General Principles While Laying Damp Proof Course
- Damp proofing course should be so laid that it should provide continuous projection.
- It should be horizontal or vertical.
- Horizontal damp proofing course should cover the full thickness of walls, excluding rendering.
- The damp proof course should not be kept exposed on the wall surface, otherwise it may get damaged during finishing work.
- When a horizontal damp proof course is continued to vertical face, a cement concrete fillet of about 75 mm radius should be provided at the junction.
- At junctions and the corners of the walls, the horizontal damp proof course should be laid continuous.
- The mortar bed supporting the damp proof course should be even and levelled and should be free from projections so that the damp proofing course is not damaged.