Causes of Dampness and Methods of Damp proofing Buildings
Dampness occurs in a building when there is moisture penetrating various parts of the building like the floor, roof, windows, and walls. If the moisture is allowed to continuously penetrate, it may leads to damage of the building and as well cause health hazards to the occupants. In this article, we shall be discussing the causes of dampness and the method of preventing or damp proofing buildings.
- Dampness due to Ground Water.
All buildings foundations are laid on the ground which is made up water. Sometimes the water level may rise due to capillary action thereby introducing water into the foundation, floor and even the walls of the building. This can cause dampness of ground floor of the building if damp proof course is not provided.
- Dampness due to Rain Water.
Rain water can penetrate into building as a result of improper sloping of the roof which results to water ponds being formed on flat roof and then water enters into the slab which remains for long time causing dampness. Improper fixing of down take pipes can also cause water to enter the roof and walls of buildings. Splashing of water on the out wall can equally cause dampness due to poor plaster coating.
- Dampness due to water leakage from Pipes.
Pipes from overhead tanks are taken over roof and along the wall. Pipes are also use to drain water from bathrooms, toilet, and kitchen. This pipes are usually joined together to get the required length and turns. As a result of this, water can easily leak through the joints introducing water into the building if there are not properly joined together.
f the building is subject to dampness by any of the above causes over long period of time, this can result to rusting of the steels in slabs and beams, disintegration of bricks and stones, crumbling of the plasters, floor covers get damaged, termite attack on wooden articles, etc.
Methods of Preventing Dampness or damp proofing
- Providing damp proof course.
Damp proof course should be provided between the source of dampness and the building component using any water repellant materials like bitumen, mastic asphalt, cement concrete, and metal or plastic sheets. The DPC should cover the full width of the wall. It should be laid on a leveled surface of mortar. The joints should be minimum and should not be at critical points. When horizontal DPC on roof is continued on vertical face of the parapet wall, the junction should be filled with about 75mm fillet of cement concrete.
- Surface Treatment.
This method of damp proofing is use when moisture in only on the superficial and not under pressure. It consists of application of the layer of water repellant compounds on the surface of walls. Most of the water proofing agents used includes; silicate, sodium, potassium, sulphates of aluminium, zinc and magnesium.
In this method, a mixture of cement and water is forced by a cement gun on the surface to be made water proof. Later, cement mortar of mix ratio 1:3 or 1:4 is applied to the surface with pressure using compressed air. Thus and impervious layer of mortar is provided.
- Providing Cavity Wall.
Cavity wall may be constructed to protect the foundation masonry and the walls. The cavity wall helps to stop moisture travelling from outer to inner wall.
- Pressure Grouting.
In this method, cement grout is forced under pressure to seal cracks in the surface of concrete.