Basics in Building Construction

Basics in Building Construction 4(2+2)

Lesson 04 : Damp Proofing : Methods And Materials

Causes Of Dampness

Absorption of moisture by the building material 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 structures or bad workmanship or by use of defective materials, moisture may find its way into interior of the building either through the wall, floor or the roof. Some of the major causes which are responsible for the entry of dampness in a building are

1. Raising of moisture from the ground
   All the structures are founded on soils, and the substructure is embedded into it. If the soil is pervious, moisture constantly travels through it. Even in the case of impervious soils, lot of soil moisture may be present. This moisture may rise up into the wall and the floor through capillary action. Ground water rise will also result in moisture entry into the building through walls and floor.


2. Exposed tops of walls
   If the wall tops are not properly protected from rain penetration, rainwater will enter the wall and will travel down. Rain can penetrate through solid brick walls as there is a limit to the amount of rain that a wall can keep out, moisture being conveyed through bricks and through mortar joints. Leaking roofs will also permit water to enter.


3. Action of rain
   Heavy showers of rain may beat against the external faces of walls and if the walls are not properly treated, moisture will enter the wall, causing dampness in the interior. If balconies and chajja projections do not have proper outward slope, water will accumulate on these and could ultimately enter the walls through their junction. This moisture travel would completely deface interior decoration of the wall.


4. Condensation
   Due to condensation of atmospheric moisture, water is deposited on the walls, floors and ceilings. This moisture may cause dampness.


5. Miscellaneous causes

   Dampness in the building may occur

   • When the structure is located on a site , where water be easily drained off,
   • Due to imperfect orientation. The walls obtaining less sunshine and heavy showers of rain are liable to become damp.
   • Due to very flat slope of a roof, that may lead to the penetration of rain water which is temporarily stored on the roof.
   • Due to bad workmanship in construction, such as defective rain water pipe connections, defective joints in the roofs, walls, etc.