A damp-proof course (DPC) is installed horizontally between courses of brick or blockwork, typically about 150mm (6 inches) above ground level.
Why is DPC Placement Important?
The DPC is a crucial element in preventing rising damp, where ground moisture is drawn up through the walls by capillary action. Incorrect placement can render it ineffective, leading to dampness problems and structural damage.
Specific Considerations for DPC Placement:
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Above Ground Level: The primary reason for placing the DPC above ground level is to protect the building from rain splash and surface water. If the DPC is at or below ground level, it will be constantly exposed to moisture, potentially compromising its effectiveness.
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150mm (6 Inches) Rule: The general guideline of 150mm provides sufficient protection in most situations. However, local building codes and site-specific conditions may necessitate a different height.
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Consider Landscaping: Be mindful of planned landscaping. Adding soil or paving that covers the DPC effectively bypasses it, allowing moisture to enter the wall.
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Relationship to Internal Floors: The DPC should generally be at least as high as the finished internal floor level to ensure the interior of the building remains dry.
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Step DPCs: On sloping sites, a stepped DPC arrangement is used to maintain the barrier at the correct height relative to the ground.
Types of DPC Materials:
Common DPC materials include:
- Bituminous Felt: A traditional and cost-effective option.
- Plastic/Polyethylene: Durable and resistant to degradation.
- Slate: A natural and long-lasting material (although less common now).
- Engineering Bricks: Dense, water-resistant bricks used as a DPC.
Ensuring Effective DPC Installation:
- Proper Overlap: When using roll-form DPC, ensure sufficient overlap at joints to create a continuous barrier.
- Mortar Bedding: Place the DPC on a level bed of mortar to provide full support.
- Avoid Punctures: Be careful not to puncture the DPC during installation.
- Professional Installation: If unsure, hire a qualified builder or damp proofing specialist.
In summary, the DPC is placed between courses of brick or blockwork, typically 150mm above ground level, to prevent rising damp. Its correct installation is crucial for the long-term health and durability of the building.
