What is Damp Proof Course (DPC)? Damp proofing materials. Causes and Treatment of DPC

 

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 In Structures

Various causes of dampness in a building are as given below:

1. Moisture Rising Up The Wall From Bottom (Ground)

All the structures have a foundation as a base to support the structure. The foundation rests on the ground. If the ground or the soil is pervious, the moisture continuously travels through it.

Also, if the soil is impervious the soil has a lot of moisture may be present in it. Through capillary action, the water rises up the wall and the floor. The water in the walls causes damage to the structure.

2. Rainwater Traveling From Wall Tops

If the top portion of the wall is not protected against penetration of water, the rainwater will enter the wall through cracks and will travel down. Leakage in roofs will also permit water to enter.

 

If there is heavy rainfall, it strikes the walls, and if the wall is not treated properly, moisture will enter the wall, causing dampness in its interior.

4. Condensation

Due to the condensation of atmospheric moisture, water is deposited on the wall, floor, and ceiling, which may cause dampness.

Other Miscellaneous Causes Of Dampness.

Moisture also enters the structure due to the following causes:

• Poor drainage at the building.
• Improper orientation of walls.
• Improper slope of roof.
• Poor construction, etc.

How To Prevent Dampness In Buildings

Below given are the methods for damp proofing a building:

1. Use of damp proof course (DPC): membrane damp proofing.
2. Integral damp proofing.
3. Surface treatment.
4. Cavity wall construction.
5. Guniting.
6. Pressure grouting.

1.     Membrane damp proofing: 

In membrane damp proofing, a  water repellent membrane is inserted between the source of dampness and the part of the building adjacent to it. Damp proofing material may be like bitumen, mastic asphalt, polythene sheets, bituminous felt, metal sheets, cement concrete, etc. damp proofing course may be provided either horizontally or vertically in floors and walls.

2. Integral damp proofing

It consists of the addition of water roofing compounds to the concrete mix so that it becomes impermeable. The principle of these compounds could be mechanical in which they feel up the words of concrete, a chemical in which they react chemically with the concrete two bodies waterproof concrete or water repulsive principle in which the added compound makes the concrete water repellent.

3. Surface treatment

 

It consists of the application of a layer of water repellent substances or compounds on the surface to be protected so that it disallows the entering of moisture. The use of water repellent metallic soaps success calcium and Aluminium plates and stearates are most effective against rail water preparation. However overall this method is effective only when the mixture is superficial and not under pressure.

Painting and plastering of the exposed surfaces must be done carefully, using waterproof agents like sodium or potassium silicates, aluminum or zinc sulfates, barium hydroxide and magnesium sulphate, etc. The surface treatment gives better results only when the mixture is superficial and not under pressure. Sometimes walls of stone and brick exposed surface is is sprayed with water repellent solutions.

4. Cavity wall construction

 

The cavity wall prevents the protection of water inside the building by shielding the main wall by an outer skin wall living a cavity between the two. It is an effective damp proofing technique.

5. Guniting

Guniting consists of depositing under pressure, and impervious layer of reach cement mortar persists of 1:3 cement sand mix which is shot on the clean surface at a distance of 75 to 90 cm with the help of a cement gun under the pressure of 2 to 3 kg/cm2. For the perfect pressure the distance between the surface to be gunited and nozzle of the machine should be kept about 75 to 90 cm from the surface. And the motor mixture of desired consistency and thickness can be deposited to get an imperious layer. This motor mix layer should be perfectly cured at least for two weeks.

6. Pressure grouting

Pressure grouting is a process of forcing cement grout, under pressure, into cracks, voids, fissures, etc. Present in the structural components of the building the consolidating them and enhancing there water penetration resistance.

This method is very sensitive and useful for checking the seepage of rising groundwater through the foundation structure of a building.

Common damp proofing materials:

The commonly used damp proofing materials are listed below:

(1)   Hot bitumen

(2)   Bituminous felt or asphaltic felts

(3)   Metal sheets

(4)   Combination of sheets and bituminous felts

(5)   Bricks

(6)    Stones

(7)   Mortars

(8)   Cement concrete

(9)     Plastic sheets