Dampness in building may occur due to bad design, faulty construction and use of poor quality of materials. This dampness not only affects the life of the building but also creates unhygienic conditions of the important items of work in the construction of a building.
The treatment given to prevent leakage of water from roof is generally termed as water proofing whereas the treatment given to keep the walls, floors and basement dry is termed as damp proofing.
Defects Caused by Dampness in Building
The various defects caused by dampness to building may be summarized as under:
- efflorescence which may ultimately result in disintegration of bricks, stones, tiles etc.
- softening and crumbling of plaster.
- bleaching and flaking of paint with the formation of coloured patches.
- warping, buckling and rotting of timber.
- corrosion of metals.
- cause deterioration to electrical fittings.
- promotes growth of termites.
- creates unhealthy living conditions for the occupants.
Causes of Dampness in Buildings
Absorption of moisture by the building materials is one of the chief causes of dampness. On account of granular nature of materials, moisture finds an easy access through the voids and this aided by capillary action assists the moisture to travel in different directions.
Thus, either on account of faulty design of structure or bad workmanship or by use of defective structures or by use of defective materials, moisture may find its way on the interior of the building either through the wall, floor or roof.
Sources of Dampness in Building
The important sources of dampness may be summarized as below:
- Dampness rising through the foundation walling – Moisture from wet ground may rise well above the ground level on account of capillary action.
- Splashing rain water which rebounds after hitting the wall surface may also cause dampness.
- Penetration of rain water through unprotected tops of walls, parapet, compound walls, etc may cause dampness.
- Sloped roofs, rain water may percolate through defective roof covering. Faulty eaves course and eave or valley gutters may allow the rain water to descend through the top supporting wall and cause dampness.
- In case of flat roofs, inadequate roof slopes, improper rainwater pipe connections, and defective junction between roof slab and parapet wall may prove to be the source of dampness.
Methods of Preventing Dampness in Buildings
Following methods are generally adopted to prevent the defect of dampness in a structure:
- Membrane damp proofing
- Integral damp proofing
- Surface treatment
- Guniting
- Cavity wall construction
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