Dampness may be caused by:
(a) Ground water
(b) Rain water and
(c) Leakages from pipes.
(a) Dampness due to Ground Water: All buildings are founded on soils. Soil holds water for a long time. Sometimes water level may rise and come in contact with foundation. Due to capillary action moisture from ground rises into foundation, floor and even in wall.
(b) Rain Water: May enter the building components due to various reasons.
(i) From wall top: If top of wall is not protected with impervious course like concrete, water can enter the wall and keep it damp for a long time.
(ii) From face of external walls: Splashing of outer wall by rain results into moisture entering the wall. Poor plaster coat is the main source of this type of dampness.
(iii) Improper fixing of downtake pipes: If downtake pipes from roof are not properly fixed, a thin layer of water stagnates near the mouth of downtake pipes. This results into entry of rain water into roof and wall.
(iv) Improper slopes to roof: In flat roofs, many times this is the cause for the dampness of roofs. If slope is not given properly, water ponds are formed on the flat roof, which results into entry of water into slab. Once water enters the slab it remains for long time creating dampness.
(v) Defective construction: Imperfect wall joints, improper slopes to chejja, construction joints in roof etc. cause dampness in buildings.
(c) Leakage from Pipes: From over head tanks, pipes are taken over roof and along the wall.
From bathrooms, toilets and kitchen water is drained out with different types of pipes. The pipes are joined to get required length and turns. Many times water leaks through joints resulting into moisture in building components.