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How to resist dampness in structure

Dampness in building is treated as one of the alarming factors throughout building design. If precaution is not taken, it can create adverse effect on the building structure as well as unhealthy condition for the dwellers in that building.

Dampness occurs due to rising of water through the walls with capillary action. Moisture may originate from the soil around the outer surface of walls or through the floor construction. Because of the capillary ‘lift through the fine pores in brickwork and masonry, moisture attains a maximum height up the wall of about 1 metre.

Main reasons of dampness in building - Dampness mainly occurs because of infiltration of water into the building components (like walls, floors, roof or basement etc).

Given below, major causes of dampness in building:

a. Substandard quality of construction material
b. Poor design
c. Imperfect construction or bad workmanship

Before utilizing various measures, the following precautions are essential to undertake:-

1. The site should have been situated on high ground and well-drained soil to get rid of from foundation dampness
2. All the uncovered walls should be built with adequate thickness to resist from heavy shower or rain (minimum 30 cm)
3. Standard quality bricks without any defects should be utilized
4. Standard quality cement mortar (1:3) should have been utilized to create distinct pattern and correct bond in the building
5. Cornices and string courses should have been arranged to prevent rain water away from the walls
6. Wrapping with water proofing cement plaster should be provided to all the uncover surfaces like top of walls, compound walls etc.
7. Cavity walls perform better as compared to solid walls in resisting the dampness

VARIOUS USEFUL METHODS:

1. Application of damp proof courses
2. Water proof or damp proof treatments
3. Integral damp proofing treatment
4. Cavity walls or hallow walls
5. Guniting or shot concrete or shotcrete
6. Pressure grouting or cementation

1. USE OF DAMP-PROOF COURSES (D.P.C.): Damp-proof courses mean layers or membranes of water repugnant materials like bituminous felts, mastic asphalt, plastic sheets, cement concrete, mortar, metal sheets, stones etc. which are provided in the building structure at all locations where infiltration of water is suspected. The best location or position of D.P.C. when the building does not contain any basement and situates at plinth level or structures devoid of any plinth level, it should be placed minimum 15cm over the ground level. The damp proof course is arranged horizontally and vertically in floors, walls etc.

2. WATER PROOF SURFACE TREATMENTS: The surface treatment comprises of filing up the pores of the material that is uncovered to moisture with the help of a thin film of water repellent material above the surface (internal / external). External treatment is mostly suitable for resisting dampness.

Various types of surface treatments like pointing, plastering, painting, distempering etc. are arranged to the uncovered surfaces and also to the inside surface. The lime cement plaster with (1:6) (1-cement, 6-lime) mix proportion is considered as the most recognized treatment to safeguard the walls from dampness. The sodium or potassium silicate are normally used as suitable water resistant agent in surface treatments. Aluminium or zinc sulphate, Barium Hydroxide and magnesium sulphate are also utilized in alternate applications. Soft soap and alum also in alternate applications, unie and unseed oil; coal tar, bitumen, waxes and fats; resins and gums Waxes and fats are not recommended because they dissolve in high temperatures.

3. INTEGRAL DAMP-PROOFING TREATMENTS: The integral treatment comprises of adding specific compounds to the concrete or mortar throughout the mixing process. These create barriers to moisture penetration under different principles when applied in construction.

i) Compounds like chalk, talc, fallers earth etc. contain mechanical action principle (i.e.,) they fill the pores existent in the concrete or mortar and transform them solid and water proof.
ii) Compounds like denser and water proof sulphates, calcium chlorides etc. function on chemical action principle (i.e.) they behave chemically and fill the pores to function as water-resistant.
iii) The compounds like soaps, petroleum, oils fatty acids compounds like sodium ammonium etc. perform on the repulsion principle i.e., they are employed as admixture in concrete to react with it and turn out to be water repellent.

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How to resist dampness in structure