Sources of Dampness

Dampness in a building may be caused due to natural causes or structural causes.

1. Natural Causes

Natural causes may be due to:

1. Penetration of rain
2. Rise of moisture from ground
3. Moisture condensation
4. Drainage condition of the site
5. Orientation of the building

(i) Penetration of Rain

Rain may penetrate a building through the top of the walls, through the surface of the walls and through the roof. Rain may penetrate the unprotected parapet walls of a building during heavy rains.

(ii) Rising of Moisture from the Ground

The ground or sub-soil on which a building is constructed may give an access to water to enter the structure and cause dampness. Gravel and sandy soil are highly permeable and allow water to pass through them easily. But clay and clayey silt or clayey sand are less permeable but cause dampness due to heavy capillary rise.

(iii) Moisture Condensation

Whenever the warm air in the atmosphere is cooled, the process of condensation takes place. Because of this condensation, moisture is deposited on the areas of walls, floors and ceilings.

(iv) Drainage Conditions of the Site

The elevation of a ground on which a building is constructed has significance on dampness condition. Buildings built on a higher ground can be drained easily and are, hence, less liable for dampness. Low-lying sites can not be drained easily and may cause water logging. The condition will get still worse if impervious soil is present beneath the structure. Hence, it is an essential condition to be looked into before starting any construction.

(v) Orientation of the Building

Depending on the climatic conditions and monsoon walls of buildings may be subjected to constant splash of rain water. Hence, the construction of a building should be accordingly planned.

2. Structural Causes

Structural causes may be due to faulty design of the building, faulty construction, poor workmanship or use of inferior quality material in construction.

(i) Faulty Design of Structure

Improper mix design of concrete not only has less strength but of high permeability causing dampness. Improper mortar proportions may also cause water penetration. Non-provision may also cause water penetration. Non-provision of a damp-proof course in the design and improper plinth-protection measures may cause dampness in the building.

(ii) Faulty Construction of Structure

Improper construction of various parts, for example, fixtures in a building, joints in the roofs, throating of sills and copings, joining of walls, etc., may cause dampness by entry of water.

(iii) Poor Workmanship and Materials

Skilled workers should be used for construction of walls, roofs, floorings, etc., and electrical and plumbing works. Further, good quality materials should be used to get effective construction.