What is Dampness ?
Dampness is the presence of moisture in the various parts of buildings such as a floor, wall, roof etc. Dampness is either formed due to inclusion from outside or condensation within the building. Dampness in the building leads to unpleasant and unhygienic conditions to dwellers thus sufficient care must be taken to prevent such situations.
Causes of Dampness in the Building.
Rain Water :
- If the rooftop of the building is not properly covered with waterproofing materials water can easily enter into the building.
- In the flat roof improper roof slopes result in the ponding of water which results in the dampness.
- If the top of the wall is not protected with the impervious layers such as concrete, water proofing admixtures etc, the rain water can be easily enter into it.
- The splashing of rain on the external surface of the water may also result in the entry of water to the wall.
- Improper plastering on the external surface may also lead to dampness.
Leakage from Drain Pipes :
If the drain pipes from the roof top are not properly fixed, water starts to pond near the mouth of the drain pipes. This also results in dampness.
Generally all the buildings are constructed upon the soil. Due to capillary action or increase in the groundwater table the water may hit the foundation. This results in the formation of dampness at the floor level.
Leakage from Pipes :
It may be commercial or residential building, there will be a number of water pipes, soil pipes etc constructed in the structure. These pipes are connected either to circulate the water or to drain off the water. The network of the pipe is created by joining a number of pipes, bends etc. which often leads to leakages of waters. This leakage of water results in the formation of dampness.
Common Material Used for Damp Proofing
Bitumen is commonly used material for damp proofing. It is generally provided to the thickness of about 3 mm over the bedding of concrete or mortar. Generally it is applied with a brush or roller.
Bituminous or Asphaltic Felt :
It is rolled flexible material provided on parapet walls and roof slabs. It is provided with an overlap distance of 100 mm on sides. Generally these laps are sealed with bitumen. These materials are not capable of withstanding heavy loads.
Mastic Asphalt :
It is a semi rigid material obtained by the heating of asphalt with sand and mineral fillers. It is generally impervious and should be laid carefully.
The bricks with water absorption less than 5% are used for damp proofing. These bricks are laid in two to five courses in cement mortar.
Stones such as granite, trap, slates etc are also used for damp proofing. These stones are laid 2 full width of the wall.
1:3 cement mortar with sufficient amount of lime and waterproofing agents are used for damp proofing. These are generally laid per suitable thickness in foundations, ground slabs, top of parapet walls etc. Sometimes it is also used in plastering external walls.
The cement concrete of thickness 75-100 mm with ratio of 1: 1.5: 3 or 1: 2: 4 is provided before constructing walls.
Metal Sheets :
Metal sheets such as copper, aluminium or lead sheets are provided to seal the construction joints. A bituminous seal must be provided for this type of proofing.
Plastic Sheets :
Plastic sheets are also a good damp proofing materials. Plastic sheets of 1 mm thickness which is made of black polythene are placed over the surface to be damp proofed.