Damp is very destructive to a building. So bad in fact the government regulations require one to take measures to counter it so as to have a certifiably habitable building. This means when building, choosing DPM is inevitable. It is wise to leave this choice to the mason or the contractor. It is however wise to familiarize yourself with the different types of DPM.

So what do you look for in damp proofing material? It should be able to hold out water i.e. impervious. After all, this is the chief use for the material. It should also be free of water absorbing salts like nitrates, sulphates or chlorides. Having these salts would invalidate its use since it is to remain water-proof. The material should also be very strong and able to withstand very heavy weights if it is to support a wall, then its strength has to be superior.

There are several categories of DPM. There are rigid materials like cement concrete, slate, engineer’s bricks. Then there are semi-rigid materials that maybe a combination of asphalt and mastic. Finally there are the flexible materials like Plastic sheets and bitumen. Chemical DPM is usually cream or liquid based on silicon and silicates. There are semi-porous materials like clay which are inserted at intervals and lose water by evaporation. Finally we have electro-osmotic proofing that operates on the principle that water is attracted to negative charge. Wires and nodes are inserted into the walls and plugged into 13amp power and these terminals attract water towards the ground thereby countering its rising and preventing damp walls

The choice of DPM also depends on where the material is to be laid. If it is just above ground level for a wall, the wall’s thickness should be factored in but generally this proofing can use any of the materials. When laying DPM on large areas like the roof or the floor, we need to minimize the joints and should go for flexible material like plastic or asphalt. Flexible material is also ideal for cavity walls especially around windows, floors. We also have areas of the building with thermal movements like the parapets. These should also have material that is strong like bitumen and asphalt.

The basic principles of choosing DPM are the strength of ingredients, flexibility, porosity and the method of application.