What is Damp Proofing?
One of the essential requirements of a building is that it should be dry. But this may not be the obvious case in most buildings as some buildings are more vulnerable to dampness and musty smell. Dampness in buildings is mainly due to bad design, faulty construction and use of poor quality of materials. Dampness not only adversely affects the life of building but also creates hygienic and health risks for the occupants. The treatment applied to keep the walls, floors and basement dry and damp free is termed as damp proofing. Damp proofing is effected by the use of a damp proof course commonly referred to as DPC.
A damp proof course (DPC) is a physical barrier inserted into the fabric of a building to stop water passing from one place to another. This can be on a horizontal plane, stopping water rising up from the ground by being sucked up by the dry masonry above, or vertically to stop water passing from the outside of a building, though the masonry, to the inside. DPC's have taken many forms through the ages and one of the earliest forms was to use a layer of slate in the construction. Slate is still used but the less expensive plastic version is now more widely used.
What Causes of Dampness?
Dampness in building is a common and universal problem. Several factors which are responsible for dampness in a structure are:
1. Rising of moisture from ground
The ground on which construction or the affected building stands may constitute of soil type which is more permeable to water. Usually the building material used for the foundations, absorb moisture by capillary action. Thus the dampness finds its way to the floor through the sub structure.
2. Exposed Walls
Wall surfaces that are not adequately protected from long exposure to heavy showers of rain eventually become source of dampness in the structure. Similarly a leaking roof also permits the rainwater to enter a structure thus resulting in dampness.
3. Condensation
The process of condensation takes place when warm humid air is cooled. This is due to the fact that cool air can contain less invisible water vapor than warm air. When the moisture deposits on the walls, floors and ceiling it results in dampness. This usually occurs in badly designed kitchen.
4. Poor Drainage
In case the building stands on a site which cannot be easily drained off then the stagnancy of the water around the building will definitely result into dampness.
5. Building Orientation
The orientation of a building is also an important factor, the wall obtaining less sunrise and heavy showers of rain are more liable to become damp.
Effect of dampness
Building material such as bricks, timbers, concrete etc., have a certain level of moisture content which is not harmful under normal conditions. But the rise in moisture content in these materials beyond the normal level to where it becomes visible leads to dampness. In absolute terms, the moisture content of different materials may be same, but the acceptable limit differs from material to material. For instance, the presence of 10 per cent by weight in timber is not harmful. But the same level could saturate a brick or cause deterioration of plaster.
The prominent effects of dampness are;
- A damp building gives rise to breeding of mosquitoes and creates unhealthy condition for those who occupy it.
- The metals used in the construction of material are corroded.
- The decay of timber takes place rapidly due to dry-rot in a damp atmosphere.
- The unsightly patches are formed on the wall surface and ceiling killing the beauty of the house.
- The materials used as floor covering are serious damaged especially in wooden floors.
- It results in softening and crumbing of the plaster.
- The materials used for wall decoration are damaged and it leads to difficult and costly repairs.
- The flooring gets loosened and easily chips off because of reduction in the adhesion when moisture enters through the floor.
Fundi Mjanja
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