Damp Proofing Course (DPC)

            Dampness is the presence of moisture on specified surface and the remedy to prevent the dampness is called damp proofing. The layer of certain materials used for damp proofing work is known as damp proofing course (DPC). The minimum vertical difference for DPC is provided 15cm above the ground level. According to requirement, it is provided in horizontal as well as vertical portion of wall.

Cause of  Dampness

Following are the main causes of dampness:-

• Hygroscopic water
• Gravitational water
• Rain beating against external wall.
• Rain travel from wall top
• Moisture rising up in wall from ground.
• Condensation of atmospheric moisture.
• Poor drainage, imperfect roof slop, defective construction

Effect of Dampness

Following are the effect of the dampness

• It gives rise to breeding of moistures and creates unhealthy hygienic condition.
• Moisture travel may cause softening and crumbling of plaster.
• Travel of moisture through walls and ceiling may cause unsightly patches.
• Effecting the decoration.
• Efflorescence effect on the wall.
• Timber fitting like doors, windows etc. get deteriorated.
• Electrical fitting get deteriorated.
• It promotes the growth of termites.
• Rusting and corrosion of metal fittings.

Method of Damp Proofing

1.Membrane Damp Proofing:- It consists of introducing a water repellent membrane or DPC between the source of dampness and the part of building adjacent to it.DPC may be flexible material (bitumen, mastic, asphalt , bituminous felt) or metal sheet,

2.Internal Damp Proofing:- It consists of inducing a certain water proofing materials  (chalk, talc, fuller-filling of void; alkaline silicate, aluminium sulphate, CaCl₂  -Chemical reaction; soap, petroleum, oil, fatty acid- water repellent) to the concrete mix, so that it becomes impermeable. Ex Sika,permo,Publo etc.

3.Surface Treatment :- it consists of  application of layer of water repellent substances or compounds on these surfaces through which moisture enters.

4.Cavity Wall:- This is an effective method of damp prevention, in which the main wall of a building is shielded by an outer skin wall, leaving a cavity between the two.

5.Guniting:- It is process of providing impervious layer of rich cement mortar over the exposed surface under pressure. The rich motor consist of cement:sand(1:2 to 1:3) and pressure is given 2 to 3 kg/cm² . The nozzle of the machine is kept at a distance of about 1m (75 to 100 cm) from the surface to be gunited.

6.Pressure Grouting:- It is the process of providing cement grouted under pressure into cracks, voids, fissures etc. present in the structural component of the building or other structure.