Water can penetrate the masonry through faulty sills, bad workmanship, etc. and hence in buildings, a layer of water repellent material called damp proof course (DPC) is introduced, which acts as a barrier against the capillary rise of water.
Sources of Dampness in Building
- Rise of moisture from the ground due to capillary action
- The action of rainwater
- Penetration of rainwater from top of the building
- Condensation due to atmospheric moisture
- Miscellaneous sources or causes like poor drainage of a building site, the imperfect orientation of a building, defective construction, etc.
Use of Defective Materials
- Contact with vegetation
- Contact with banked earth
- Defective roofs and gutters
- Defective window sills
- Defective parapet wall
- Rising moisture due to capillary action, through walls and floors
- The splashing of water on wall surfaces.
- Leakage of the site which may result in waterlogging, and ultimately, it may result in dampness in a building.
- Improper drainage of roof and leakage through roof & roof joints.
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Effects of Dampness in Building
The structure is badly affected by dampness. The prominent effects of dampness are as follows:
- A damp building creates unhealthy conditions for occupants and also gives rise to the breeding of mosquitoes.
- Corrosion of metals used in the construction of the building may take place.
- The unsightly patches are formed on the ceilings and walls surfaces.
- The decay of timber takes place rapidly due to dry-rot in a damp atmosphere.
- It results in 1:1 softening and crumbling of plaster.
- It promotes the growth of termites.
- The walls may cause efflorescence, which may result in the disintegration of stones, bricks, tiles, etc. and the strength of the wall is then reduced.
- The materials used as floor coverings are seriously damaged.
- The electric fittings deteriorate, and it may lead to a danger of short-circuiting.
- Unhealthy living for the occupants prevails in a damp building.
- Efflorescence on building surfaces takes place, causing the disintegration of the bricks, stones, tiles, etc. and thus useful life of a building is being lost.
- It causes bleaching of paint, which results in the formation of coloured patches on wall and ceiling surfaces.
- It results in softening and crumbling of plaster.
- Timber, when it comes in contact with water, gets deteriorated due to warping, buckling, and rolling.
- Dampness promotes the growth of termites.
- The surface of the wall is affected patches. Are seen on walls. The point false off, and colours get faded.
- The building elements made up of timer distorted in their dimensions. The timber may decay.
Causes of Dampness
The dampness in a building is a general problem. the various causes which are responsible for the entry of dampness in a structure are as follows:
- Rising of moisture from the ground
- Action of rain
- Exposed tops of walls
1. Rising of Moisture from the Ground
The ground on which the building is constructed may be made of soils which easily allow the water to pass.
Usually, the building materials used for the foundations absorb moisture by capillary action. Thus the dampness finds its way to the floors through the substructure.
2. Action of Rain
If the faces of the wall, exposed to heavy showers of rain, are not suitably protected, they become the sources of entry of dampness in a structure.
Similarly, the leaking roofs also permit the rainwater to enter a structure.
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3. Exposed Tops of Walls
The dampness may also enter through the exposed tops of the parapet walls and compound walls.
Thus, the exposed tops of such walls should be provided with a damp proof course on their exposed tops.
Cool air, contain less invisible water vapour than warm air. The process of condensation takes place when warm, humid air is cooled.
The moisture is deposited on the walls, floors, and ceilings. This is the main source causing dampness in badly designed kitchens.
Defective roof covering of the pitched roofs. Defective junctions between roof slabs and parapet walls. Inadequate slopes in roof slabs.
Improper rainwater pipe connections.