You should use a damp proof membrane (DPM) when you need to create a barrier against moisture transmission between a concrete or screed subfloor and a wood floor (or other moisture-sensitive flooring).
Here's a more detailed explanation:
DPMs are crucial for protecting flooring materials that are susceptible to damage from moisture rising from the ground or through the concrete slab. Without a DPM, moisture can lead to:
- Warping and cupping of wood floors: Excess moisture causes wood to expand and contract unevenly, leading to these deformities.
- Mold and mildew growth: Damp conditions create a breeding ground for these harmful organisms, impacting indoor air quality.
- Adhesive failure: Moisture can weaken the bond between the subfloor and the flooring adhesive, causing the flooring to detach.
- General deterioration of flooring materials: Prolonged exposure to moisture can significantly shorten the lifespan of your flooring.
Therefore, a DPM is essential in the following scenarios:
- New Concrete Slabs: Newly poured concrete slabs contain a significant amount of moisture that needs to be blocked before installing flooring.
- Below-Grade Applications: Basements and other below-grade areas are naturally prone to higher moisture levels.
- On-Grade Applications: Even on-grade slabs can be affected by rising damp, especially in areas with high water tables or poor drainage.
- When Installing Moisture-Sensitive Flooring: Materials like solid hardwood, engineered wood, laminate, and even some types of tile require protection from moisture.
- Uncertainty about Slab Moisture Content: If you are unsure whether the concrete slab is sufficiently dry, it's always best to err on the side of caution and install a DPM. Conducting a moisture test of the slab is highly recommended.
In summary, utilize a DPM whenever there's a risk of moisture migration affecting your flooring installation, particularly when installing wood or other moisture-sensitive materials over concrete subfloors. It's a preventative measure that protects your investment and ensures the longevity of your flooring.
