Dampness is defined as the presence of hygroscopic moisture in the building is called dampness. It causes serious damages to the building and effect badly the health and comfort of the occupants of the building.
Source of Dampness
Various known sources of dampness are listed as follows:
1. Heavy Rain Showers
Heavy rain showers on a building may cause dampness because most of the buildings do not with stand it and rain water penetrates through the mortar joints of the wall.
Moisture from wet ground below foundation may rise above ground level on account of capillary action and cause dampness.
3. Salt Water
Presence of salts in the water used in the construction work also cause dampness. Sodium chlorides, nitrates and chlorides of alkalies metals cause dampness.
4. Rain Water
Percolation of water through roof coverings may allow the rain water to cause dampness due to faulty eaves gutters and eave courses.
5. Drainage System
Drainage of site in a building constructed at low lying area may not be good and may create water logged conditions, thus causing dampness.
Defective construction of joints in roofs, coping improper jointing of walls etc. also cause dampness.
Atmospheric conditions are also the source of dampness.
The dampness causes corrosion of metals used in construction, crumbling of plasters, disfiguring of bricks and stones, disintegration of the floors, blistering and bleaching of paints and unhygienic conditions for the occupants. It also spoils the materials kept in cup boards, wardrobes etc. It also cause deterioration of electric installations.
Prevention of Dampness
The various methods used for the prevention of dampness are as under:
1. Integral Treatment
In this method water proofing materials/compounds are added during the process of mixing the constructional materials. Chalk, tale or feller’s earth is used which fill the pores of mortar. Concrete is made water repellent by the use of soap solution, calcium and petroleum oils etc. Pudlo, permo, sika etc., are the commercial forms of compounds which are used after diluting with water.
2. Surface Treatment
Joints in the brickwork or stone work on exposed surface are pointed while inner surface of walls is plastered. Paints, oil, waxes and soap solution etc., are also used for surface.
3. Membrane Damp Proofing
This is done by providing a layer of water repellent material between the sources of dampness and part of the structure adjacent to it, these are called damp proof course.
4. Cavity Wall Construction: By construction cavity walls, main walls in the building can be saved by the outer skin wall. The cavity between two walls prevents the moisture from reaching the inner wall.
Proper Treatment to Expansion and Construction Joints
The expansion joints and construction joints in the building should be properly sealed by water proofing materials to obstruct the leakage of water. Various types of expansion joints.
1. Expansion joint in flat roof twin kerb type.
2. Expansion joint with tee iron tile and terrace construction in level with roof surface.
3. Expansion joint with R.C.C Slab on roof surface.
4. Raised type expansion joint.