Damp Proof Course

Damp proof course is abbreviated to DPC and is the horizontal barrier in the wall which is designed to prevent moisture rising through the structure by capillary action and this phenomenon is called as rising damp. In construction work, damp proofing is said to be water proofing that is applied to the building foundation walls to prevent the wall from moisture into the interior space; Damp proof membrane (DPM) performs a same kind of functions for the solid floor.

To rise by capillary action; brick, stone, and mortar are allowing damp from ground, carrying with it ground salts including chlorides and nitrates. These salts will absorb moisture from the atmosphere which is leading to wall dampness in conditions of high relative humidity.  Building standards, especially for new buildings, at the time of construction it is necessary to incorporate Damp Proof Course. This will consist of a thin strip of plastic, a course of engineering brick or a layer of bitumen.

Materials used

The materials widely used for damp proof course includes,

• Stones.
• The flexible materials like hot bitumen, plastic sheets, bituminous felts, sheets of lead, copper, etc.
• Semi rigid materials like mastic asphalt.
•  Mortar with water proofing compounds.
• Coarse sand layers under floors. Continuous plastic sheets under floors.
•  Strong materials like impervious bricks, stones, slates, cement mortar or cement concrete which is painted with bitumen, etc.

Construction of DPC

DPC is the thick plastic strip which is bedded into the mortar in-between the two courses of bricks. Often it can be seen as the thin plastic line in the mortar near ground level. For the continuous barrier, DPC and DPM are welded together. In addition DPC is welded to the DPM around the outside edges of the ground floor, which is completely sealing the interior of the building from the damp.

In the cavity wall, usually a DPC is present in both the outer and inner wall. It is normally 150 – 200mm above ground level, in the outer wall. This will cause the rain to puddles and splash up off the ground, without saturating the wall above DPC level, but the wall below the DPC will be saturated in rainy water. The DPC in the inner wall will be normally below the floor level, or it is usually found above the floor slab so that it can link to the DPM under the floor slab.

Questions:

• What is DPC?
• What are materials used in DPC?