Guideline for laying DPC

As the foundation of all the buildings are embedded in the soil. As bricks being porous and which are generally used in foundation below ground level can absorb moisture from adjacent ground or soil. The moisture travels up from one course to another by capillary action and can make the wall damp for a considerable height. Rise in ground water table in the rainy season may aid the entry of moisture in to the wall and in the floor.

To prevent water absorbed from the soil rising and causing dampness in the wall and adjacent wood work and plaster, a continuous layer of an impervious material is provided. This layer is known as horizontal damp-proof course (DPC). The damp-proof course should be laid at plinth level i.e. at floor level in all building except temporary structures. The plinth level of the building should 45cm above the ground. On the outer walls the DPC is laid at the ground level, to save wall from dampness of floor, vertical DPC is laid on the outer walls on internal surface from ground to plinth level.

The thickness of horizontal DPC for boundary wall is 25mm and for building is 40mm or 50mm. The DPC is consists of cement concrete 1;2;4 i.e. 1 is cement, 2iscoarse sand and 4 is stone aggregate or BAZRI. The DPC should in full width of wall and should not be set back from the face of wall for pointing. It must be continuous for the whole length of the building. There should be no any construction joints in the damp-proof course. The DPC is not carried across doorways and openings.

• Before laying the DPC the surface of brick or stone masonry should be in level.
• See that the edge of DPC should be straight, even and vertical.
• The side shuttering should consist of steel form.
• Ensure that the side shuttering is strong enough so that does not get disturbed while laying and compacting the concrete mix.
• The side shuttering should be tight so that mortar/ concrete mix should not leak from the side.
• The cement concrete mix ratio should be 1;2;4 and see that all the gradients such as cement, fine aggregate, coarse aggregate and water should be according to specification.
• The cement concrete mix should be of workable consistency and should be tamped thoroughly to make a dense mass.
• See that the side surface should be smooth without honeycombing.
• The DPC should be cure for 7 days after which it should be allowed to dry for at least one day before application of bitumen.
• Before application of bitumen, the dried surface of DPC is cleaned with brushes and finally with a piece of cloth soaked in kerosene oil before application of hot bitumen.

Apply the hot bitumen in two coats uniformly at the rate of 1.7 kg per square meter all over, so that no blank spaces are left anywhere on the DPC.