In 2023, around 3.8% of homes inspected in England were found to have damp problems of some kind, equating to approximately 912,000 homes. This highlights the importance of protecting against the damage and potential health problems damp and mould can cause.
Installing a damp-proof membrane (DPM) is one way you can do just that. It prevents moisture from penetrating internal walls and floors and protects against problems that can be a consequence of moisture, such as mould and rot. It can make a huge difference to moisture problems in a home, which is what makes it one of the most reliable damp-proofing solutions a property can have.
Prokil are the South’s leading specialists in damp proofing solutions. Below, we explore the purpose of damp-proof membranes, what makes them so effective, and how to install one.
Purpose of damp-proof membranes
A DPM serves as a barrier against moisture or water vapour, preventing it from seeping into buildings or structures from the ground. Its primary purpose is to protect building materials, such as floors or walls, from damp, which can lead to various issues like mould growth, decay, or damage to the structure.
As well as being used as a damp-proofing solution and protecting the building materials, DPMs, especially those used under floors, can contribute to improving thermal efficiency. They prevent moisture from reaching insulation or underfloor heating systems, ensuring their effectiveness. They also improve air quality, as damp and mould growing due to moisture can negatively impact respiratory health.
How it works for damp-proofing
A DPM works as a barrier to prevent moisture from passing through it.
Because it’s composed of plastic, a DPM will stop water from seeping in. Sheet membranes are used as DPMs for floors, while studded sheet membranes are used for walls, with a mesh thermic welded to the surface to enable direct plaster application. These wall membranes must be vented because the studded profile creates an air gap that allows moisture to evaporate while protecting the wall.
There’s a difference between damp proofing and waterproofing that should be considered. If you’re working on a structure below ground, it’s recommended that you use a professional to design and place a system that will follow standards and regulations set by the government building regulations recommendations.
There are five parts to the workings of a DPM, which remain the same no matter where the membrane is placed or its thickness:
- Material Selection: DPMs are typically made of materials impermeable to water or moisture, such as high-density polyethylene (HDPE), bitumen-based products, or synthetic membranes. These materials are chosen for their ability to resist water penetration.
- Installation: DPMs are installed during construction at vulnerable points, such as beneath concrete slabs, floors, or within walls. The installation location depends on the specific requirements of the building design and the expected sources of moisture.
- Barrier Effect: Once installed, the DPM forms a continuous barrier that blocks the passage of moisture or water vapour from the ground. It prevents rising dampness, where groundwater or soil moisture migrates upwards through porous materials like concrete or masonry.
- Impermeability: The DPM’s impermeable nature ensures that moisture cannot pass through it, effectively stopping it from reaching building materials susceptible to moisture-related damage, such as timber, insulation, or interior finishes.
- Maintenance of Integrity: Proper installation and maintenance of the DPM are crucial. Any punctures, tears, or damage to the membrane can compromise its effectiveness. Therefore, care is taken during construction to avoid damaging the DPM, and periodic checks ensure its ongoing integrity.
- Complementary Measures: DPMs are often used in conjunction with other moisture management strategies, such as adequate drainage systems, proper site grading, and ventilation, to further mitigate moisture-related issues.
By creating a barrier against moisture, DPMs help maintain a dry and healthy indoor environment, protect structural integrity, and prevent issues like mould growth, decay, or damage caused by dampness. Their installation is a key preventive measure in construction to safeguard buildings against the damaging effects of moisture.
The installation process
The installation process for a DPM involves several steps and considerations to ensure its effectiveness in preventing moisture ingress. Here’s an overview of the typical installation process:
- Surface Preparation: Before installing the DPM, the surface where it will be laid will be cleaned, smoothed, and freed of debris, ensuring proper adhesion and a smooth surface for the membrane.
- Choice of DPM: The appropriate type of DPM will be selected based on the specific requirements of the construction project. DPMs come in various materials like polyethylene sheets, bitumen-based membranes, or synthetic materials, each suited for different applications.
- Positioning and Cutting: The professional will roll out the damp-proofing membrane sheets over the prepared surface, ensuring that they cover the entire area where moisture ingress is a concern. Sheets should overlap by a certain amount (usually around 150mm) at joints or seams, and any excess material should be trimmed accordingly.
- Fixing and Sealing: Then they will secure the DPM in place using appropriate fixing methods, such as adhesives, tapes, or mechanical fixings. Seams and joints between DPM sheets should be properly sealed using compatible tapes, adhesives, or heat welding methods to create a continuous barrier.
- Protection and Integration: Once installed, the DPM will need protection against damage during construction activities. It’s often covered with protective layers, such as screed, concrete, or insulation materials depending on its location and intended use within the structure.
- Quality Checks: Checks will need to be conducted to ensure the integrity of the installation, examining for any tears, punctures, or areas of weakness that could compromise the DPM’s effectiveness. Any issues will need to be addressed immediately to maintain the membrane’s integrity.
- Coordination with Other Trades: Coordination with other tradespeople, such as electricians or plumbers, is important to ensure that subsequent work does not damage or compromise the DPM’s integrity.
Proper installation of a DPM is crucial to its effectiveness in preventing moisture ingress. Attention to detail, compatibility of materials, and adherence to construction best practices are essential for a successful installation.
If you’re looking for help when damp-proofing your property, get in touch with our team! We’re experienced in DPM installations and will provide a professional, efficient, and cost-effective service at every stage of the process.