Installing a damp proof membrane (DPM) on a concrete floor is crucial for preventing moisture from rising through the floor and causing damage. Here's a step-by-step guide:
1. Prepare the Concrete Surface
- Clean thoroughly: Remove any debris, dirt, dust, grease, or existing flooring. A clean surface is essential for proper adhesion.
- Repair imperfections: Fill any cracks or holes in the concrete with a suitable concrete repair compound. Ensure the surface is as smooth and level as possible.
- Allow to cure: Ensure any repair compounds are fully cured before proceeding.
2. Measure and Cut the Damp Proof Membrane
- Measure the area: Accurately measure the entire floor area you need to cover.
- Cut the DPM: Cut the DPM to size, allowing for overlaps of at least 150mm (6 inches) at the seams and around the perimeter. It's better to have too much than too little.
3. Apply Primer (Optional, but Recommended)
- Choose a suitable primer: Select a primer recommended by the DPM manufacturer or a general-purpose concrete primer.
- Apply evenly: Apply the primer to the concrete surface using a roller or brush, following the manufacturer's instructions. Primer enhances adhesion between the concrete and the DPM.
- Allow to dry: Let the primer dry completely before proceeding.
4. Lay Out the Damp Proof Membrane
- Position carefully: Carefully position the DPM, ensuring the overlaps are correctly aligned (at least 150mm).
- Avoid wrinkles: Smooth out any wrinkles or air bubbles as you lay the membrane.
- Consider underfloor heating: If installing underfloor heating, consult the heating system's guidelines, as the DPM placement might differ.
5. Secure the Membrane
- Tape the seams: Use waterproof tape (such as jointing tape specifically designed for DPMs) to seal all seams and overlaps securely. This creates a continuous barrier against moisture.
- Seal the perimeter: At the edges of the room, the DPM should ideally be turned up the wall and secured. This can be achieved with sealant or appropriate tape. The DPM should ideally reach above the level of the finished floor.
6. Trim Excess Membrane
- Carefully trim: Once the membrane is securely in place, carefully trim any excess DPM along the perimeter of the room using a sharp utility knife. Be careful not to damage the underlying DPM.
7. Install Final Flooring
- Follow flooring instructions: Install your chosen flooring (e.g., screed, insulation, final floor covering) according to the manufacturer's instructions. The DPM now forms a barrier between the concrete subfloor and your new flooring.
8. Inspect and Seal Gaps
- Thorough inspection: Inspect all seams and edges for any gaps or imperfections.
- Seal any gaps: Seal any remaining gaps with waterproof sealant or tape to ensure a complete moisture barrier.
By following these steps, you can effectively install a damp proof membrane on a concrete floor, protecting your building from moisture damage and ensuring a long-lasting, healthy indoor environment.
