DPC (Damp Proof Course) is laid by ensuring it covers the full thickness of the wall (excluding rendering) on a level and even mortar bed free from any projections. This provides a horizontal barrier to prevent rising damp.
Here's a more detailed breakdown of the DPC laying procedure:
Preparation is Key
- Mortar Bed Preparation: Before laying the DPC, a level and even mortar bed must be prepared. This bed acts as a smooth base. Ensure it is free from any stones, debris, or projections. An uneven base can damage the DPC material and compromise its effectiveness.
- Wall Surface Cleaning: The top surface of the wall where the DPC will be laid must be cleaned thoroughly. Remove any loose mortar, dust, or debris. This ensures proper adhesion of the DPC to the wall.
DPC Installation
- Material Selection: Choose the appropriate DPC material for the application. Common materials include bitumen, plastic, or slate. Select a material suitable for the wall type and exposure conditions.
- Cutting to Size: Cut the DPC material to the required length, ensuring it covers the full width of the wall excluding rendering. Accurate cutting is crucial for proper damp-proofing.
- Laying the DPC: Carefully lay the DPC material onto the prepared mortar bed. Ensure it is positioned correctly and extends fully across the wall's width. Overlap joints, if required by the material, to create a continuous barrier.
- Sealing Joints: If using multiple pieces of DPC, properly seal the joints between them using appropriate methods, such as heat welding for plastic DPC or bitumen sealant for bitumen DPC. Properly sealed joints are critical to avoid moisture ingress.
- Mortar Bed Above DPC: After laying the DPC, a further mortar bed should be laid on top of the DPC. This helps to protect the DPC and provides a level surface for the next course of bricks or blocks.
Important Considerations
- Full Wall Thickness: Ensure the DPC covers the full thickness of the wall (excluding any rendering that will be applied later). This prevents moisture from bypassing the DPC layer.
- Level Installation: The DPC must be laid perfectly level to prevent water from pooling or tracking across the wall. Use a spirit level during installation to ensure accuracy.
- Avoid Damage: Take care not to damage the DPC during installation or subsequent construction. Punctures or tears can compromise its effectiveness.
- Correct Height: DPC should be installed at least 150mm above ground level to prevent splashing water from bridging the DPC.
By following these steps, you can ensure that the DPC is laid correctly, providing effective protection against rising damp and preserving the integrity of the building structure.
