Basics in Building Construction

Basics in Building Construction 4(2+2)

Lesson 05 : Damp Proofing Treatments

Damp - Proofing Treaetment To Foundations

Depending upon the depth of the ground water level, the treatment to be given to the foundations differ and these are discussed under the following heads.

1. Treatment to foundations on ordinary soil

Building foundations on ordinary soil where the sub- soil water table is not high are also liable to get damp. Bricks being porous, brick masonry below ground level can absorb moisture from adjacent ground. This moisture travels up from one course to another by capillary action and can make the wall damp for a considerable height. This can be checked by providing Damp proof course (DPC) at appropriate place.

For normal buildings the best portion for damp-proof course lies at plinth level. Damp Proof Course should be provided at least 15 cm above the ground level. If the damp – proof course is laid just at the ground level, earth, dust or leaves might accumulate outside the wall and by the passage of time the level of outside earth may be raised above the damp proof course level. In such a case moisture can travel from outside ground level to brickwork above damp proof course and hence the purpose of providing damp proof course will not be served.

2. Treatment to foundations on damp soil

   In case of building constructed on damp soil in wet areas, both the walls as well as the ground floor are liable to become damp due to capillary rise of moisture from ground. In such cases the damp proof course is laid over the entire area of ground floor including wall thickness. Bitumen felts can be used for damp-proofing treatment. The sequence of steps for laying damp proof course are

   1. Apply hot bitumen at the rate of 1.5 kg / m 2 over the prepared surface to serve as primer coat.
   2. Lay bitumen felt in single layer over the primer coat.
   3. Apply hot bitumen at the rate of 1.5 kg / m2 over the bitumen felt to serve as finishing coat.

   Immediately after laying, the damp proof course is protected with a course of bricks laid flat on a cushion of fine sand. This prevents damage to damp proof course specification on account of droppage of sharp edged implement or other materials during construction.