For specifiers and architects, cold-applied liquid waterproofing membranes based on PMMA (Polymethyl Methacrylate) technology offer a compelling combination of performance, practicality and long-term value. But what sets PMMA apart, and why is it fast becoming the technology of choice for the most demanding applications?
For specifiers and architects, cold-applied liquid waterproofing membranes based on PMMA (Polymethyl Methacrylate) technology offer a compelling combination of performance, practicality and long-term value. But what sets PMMA apart, and why is it fast becoming the technology of choice for the most demanding applications?
PMMA is a high-performance, liquid-applied resin technology that cures to form a seamless, fully bonded waterproof membrane. Unlike traditional sheet or torch-applied systems, PMMA is cold-applied, meaning it requires no open flames or hot works during installation. This significantly enhances on-site safety, particularly on live sites or sensitive buildings.
Curing is achieved through catalyst activation, allowing PMMA systems to cure rapidly – typically within 30 to 60 minutes – even at low temperatures. This makes PMMA especially well-suited to fast-track projects and year-round installation, reducing programme risk and costly delays.
From a performance perspective, PMMA delivers where many conventional systems struggle. Its liquid nature allows for a flexible and seamless application, forming a continuous membrane with no joints, laps or welds – often the weakest points in traditional waterproofing systems. This makes PMMA ideal for complex detailing, penetrations and changes in geometry.
Once cured, PMMA membranes retain elasticity and crack-bridging capability, accommodating minor substrate movement without compromising waterproof integrity. This is particularly important in refurbishment projects or areas subject to thermal or structural movement.
Durability is another defining advantage. PMMA maintains flexibility across an extreme temperature range, from approximately -30°C to +90°C, and offers excellent resistance to UV exposure, weathering, chemicals and mechanical stress. For exposed environments such as roofs, balconies and terraces, this long-term resilience is critical.
Sustainability is no longer optional, and PMMA aligns well with modern environmental goals. The technology emits very low levels of volatile organic compounds (VOCs), improving air quality on site and for building occupants. Its long service life reduces material consumption and waste over the building lifecycle, supporting resource efficiency.
Light-coloured PMMA membranes offer high Solar Reflectance Index (SRI) values, often above 80, compared to dark bituminous membranes with SRI values as low as 0–30. Higher reflectance reduces heat absorption, lowers cooling demands, and improves overall energy efficiency.
Importantly, cold-applied PMMA avoids the combustion of fuels such as LPG, which emits approximately 2.98 kg of CO₂ per kilogram burned. Removing hot works from installation, therefore, also contributes to carbon reduction on site.
Being cold-applied, PMMA eliminates the risks associated with torch-on systems. Versatility further strengthens PMMA’s appeal. It bonds effectively to a wide range of substrates, including concrete, asphalt, metal and timber, making it suitable for both new-build and refurbishment projects.
PMMA is also commonly specified for green roof systems. As the primary waterproofing layer, it provides a fully watertight and root-resistant barrier, protecting the structure below without leaching harmful chemicals into the environment. When combined with vegetation layers, PMMA contributes to extended roof life, improved thermal performance and reduced urban heat island effects. Lower surface temperatures can even improve the efficiency of rooftop solar panels, which can lose up to 20% efficiency at higher temperatures.
BBA certification assures performance, durability and service life, while Environmental Product Declarations (EPDs) offer transparent data on environmental impact. Fire performance is tested to EN 13501 standards, with systems achieving strong classifications such as BROOF(t4), supporting compliance with UK and European fire regulations.
For architects and specifiers seeking a waterproofing system that balances performance, safety, speed and sustainability, PMMA technology represents a proven, future-ready choice. By specifying PMMA, you are not only protecting the building envelope but also delivering long-term value across the lifecycle of the project.
WestWood offers a comprehensive, end-to-end approach that supports projects from concept to completion. This includes specification support, system design, training, technical guidance, and ongoing project assistance to ensure the chosen solution performs as intended.
WestWood Liquid Technologies offers a RIBA-approved CPD, available free of charge, which can be delivered in-house, via Microsoft Teams or at your offices – please get in touch with Vicky Ramwell, Business Development Manager at WestWood to find out more, and book your session to secure valuable CPD hours. For examples of WestWood’s award-winning projects, visit its website.
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