Damp proof membranes (DPMs) are critical barriers which form an impermeable layer to block moisture migration. They protect buildings from groundwater, rising dampness and water vapour.
DPMs are available as polythene sheets, liquid-applied systems and self-adhesive membranes. Sheet DPMs offer uniform thickness, while liquid DPMs deliver seamless coverage.
How Does the Thickness of a DPM Membrane Affect its Performance?
The thickness of a DPM membrane directly impacts its effectiveness in moisture prevention. Thicker membranes generally offer better resistance to water vapour transmission and physical damage. They provide enhanced durability, especially in high-stress areas.
However, a thicker DPM isn't always better. The ideal thickness depends on specific project requirements and site conditions. Extremely thick membranes can be harder to install and may not be necessary for all applications.
Also, thicker DPMs can be less flexible. This makes it more difficult to form around corners and details where movement might happen.
What Are the Pros and Cons of Using a Liquid DPM for Floors Compared to Sheet Options?
Pros of liquid DPM
- Seamless application, reducing the risk of weak points
- Easily conforms to irregular surfaces
- Can be applied in tight spaces
- Often faster to install over large areas
Cons of liquid DPM
- Requires careful substrate preparation
- Curing time can delay further work
- May be more expensive for small areas
- Quality depends heavily on proper application technique
Sheet DPMs offer consistent thickness. However, they can be challenging to fit around complex shapes and may have weak points at seams.
How Do I Integrate a DPM for Walls With the Floor DPM for Continuous Protection?
Integrating wall and floor DPMs is key for comprehensive damp proofing. Start by installing the floor DPM, and extending it up the wall by at least 150mm. Overlap this with the wall DPM, ensuring a minimum 100mm overlap.
Use compatible sealants or tapes at the junction to create a watertight seal. Pay extra attention to corners and joints, as these are common weak points. Consider using preformed corner pieces for added protection in these critical areas.
5 Top Pro Tips on Preparing a Substrate Before Applying a Liquid Epoxy Damp Proof Membrane
- Thoroughly clean the surface, removing all dust, debris and loose materials. Use industrial vacuums or pressure washing for the best results
- Repair any cracks or damaged areas in the substrate before application. Fill cracks with epoxy filler and allow it to cure fully
- Ensure the substrate is completely dry; use moisture metres to confirm acceptable levels. Allow at least 24 hours after cleaning or repairs for thorough drying
- Apply a primer to improve adhesion. Choose a primer compatible with both the substrate and the liquid DPM
- Check ambient conditions; temperature and humidity can affect curing and performance. Ideal application temperatures are typically between 10°C and 30°C
How Do I Address Penetrations Through a DPM Sheet Without Compromising its Effectiveness?
Addressing penetrations through a DPM sheet requires careful attention to detail. First, cut the membrane tightly around the penetration. After, apply a compatible liquid waterproof membrane or specialised sealing collar around the penetration.
For pipes, use pre-formed pipe collars designed for use with DPMs. These deliver a secure, flexible seal. For irregular penetrations, create an upstand around the object and seal it with a liquid DPM or mastic.