People often seem not to care or forget about rendering their buildings damp-proof. This could be primarily because of lack of awareness on the issue. Most people apparently are either unaware of the potential adverse impacts of dampness in their buildings or some of them possibly simply ignore it as a minor issue until it is too late. While most major or modern buildings such as modern residential or mixed-use skyscrapers, malls etc. may be addressing this aspect quite seriously and effectively, the same is often not the case for common residential, official or commercial buildings.
The consequences of ignoring this small yet important aspect of building construction show up sooner or later depending upon the severity of dampness. Some of the evils of dampness creeping in unprotected buildings are: gradual swelling and crumbling of plasters, deteriorating of materials such as bricks, stones, concrete blocks etc. due to efflorescence, ugly patches on building surfaces, gradual swelling and flaking of paints etc. Besides encouraging growth of termites as well as resulting in unhealthy living condition, dampness may also adversely affect the timber & metallic elements of the structures.
There are many methods and materials available for damp-proofing buildings which keep improving with time. Modern high-class or high-tech buildings may see use of elaborate, expensive and latest techniques and materials in order to render them almost complely damp-proof. However, for ordinary buildings simple and less expensive methods are available to protect them from the claws of dampness which otherwise could easily become a major irritant in the course of time. Here, such a method, which involves providing a Damp-proof Course (DPC), is briefly explained for the benefit of the readers.
Where dampness is low but can’t be ignored, a 1.5 inch thick layer of concrete of mix ratio 1:2:4 may be laid at the plinth level of the building. This layer should be laid on the top of a freshly-laid smooth mortar bed. After the concrete layer hardens sufficiently, a coat or two of hot bitumen may be applied on it’s dry surface.
Where the dampness problem is moderately severe, the thickness of the layer may be increased to 2 inch and the concrete mix ratio to 1: 1.5 : 3. Additionally, water proofing compounds, which are readily available in the market, may also be added to the mix as prescribed in their packets itself. As mentioned above, a coat or two of hot bitumen would certainly do better. For moderately sever condition, one may opt to provide DPC under the ground floor as well. Mastic asphalt or bitumen felts are some of the commonly used materials for that purpose.
It is to be noted that the DPC should be laid in a continuous layer through the full length of the wall and the width of DPC should be same as the thickness of the wall. Lap joints, where unavoidable, for any DPC course should be rendered leak-proof with bitumen.
For severe dampness conditions such as heavy rains or raining most of the year, swampy or highly moist sub-soil condition, very high ground water level etc. superior techniques or additional measures over and above the already mentioned such as damp-proofing of external wall surfaces, roof etc. may as well become necessary.