A Damp Proof Course (DPC) is used under walls to prevent rising damp.
Understanding Rising Damp
Rising damp occurs when moisture from the ground is drawn upwards through the walls due to capillary action. This is similar to how a sponge absorbs water. Without a DPC, this moisture can climb up the wall, often reaching a height of 500-600mm (approximately 20-24 inches) above the floor level.
The Role of a Damp Proof Course
The DPC acts as a barrier, interrupting the capillary action. It's typically a horizontal layer of waterproof material built into the wall, near the base, that prevents the moisture from rising any further. Think of it as a dam stopping water flow.
Consequences of Not Having a DPC
The absence of a DPC can lead to several problems:
- Damp Patches: Unsightly and potentially damaging damp patches appear on walls.
- Damage to Plaster and Paint: Moisture causes plaster to crumble and paint to peel.
- Mold Growth: Damp conditions encourage mold growth, which can be harmful to health.
- Structural Damage: Prolonged dampness can weaken the wall structure.
- Increased Heating Costs: Damp walls are colder and require more energy to heat.
Materials Used for DPCs
Various materials can be used for DPCs, including:
- Slate: A traditional and durable material.
- Bituminous Felt: A flexible and cost-effective option.
- Plastic (Polyethylene): A modern and waterproof material.
- Chemical Injection: A method of injecting a waterproof solution into existing walls that lack a DPC or have a damaged one.
DPC Installation
The DPC is typically installed during the construction of a building. For existing buildings without a DPC or with a failing DPC, remedial measures such as chemical injection can be employed.
