Bring in the Reinforcement

Reinforced flat roof

Reinforcement within cold-applied liquid waterproofing membranes: How a reinforcement layer, or lack thereof, can make or break your roofing project. 

One of the primary considerations when specifying a liquid waterproofing membrane for a flat roof, is selecting a system that contains a reinforcement layer. Oftentimes, due to the broad range of flat liquid waterproofing systems available on the market, this can create confusion as to which is the most appropriate for your project. Whilst performance benefits differ between varying waterproofing membranes, in this article, we discuss the importance of selecting a liquid flat roofing system that includes a reinforcement layer and how it will increase the roof’s integrity and longevity. 

Reinforcement Layer: The Whys and Wherefores 

The envelope of a building needs to accommodate structural movement to prevent issues from arising, such as cracking. The roof is no exception to this and when specifying a waterproofing membrane, it is important to consider how the specified system will perform in conjunction with the substrate to accept building movement. This necessitates the inclusion of a reinforcement layer, as without such, the roof system is consequently exposed to performance issues and potential failure.  

Reinforcement layers within cold-applied liquid waterproofing membranes are designed to increase the tensile strength of the system and subsequently reduce its elasticity, thus improving the overall performance of the membrane. Usually comprised of either glass fibre matting or polyester fleece, the reinforcement layer helps to cope with the structural movement of substrate, reducing the level of stress incurred by the membrane at heightened risk areas, including movement cracks, expansion joints, and upstands. Ultimately, this mitigates the risk of damage to the membrane, as the reinforcement layer bolsters the adhesion between the system and substrate.  

Whilst there are non-reinforced waterproofing membranes commercially available, these are generally advised against, due to the reduced capability of accepting the stresses encountered on a roof, in addition to structural issues and subsequent costly repairs. If a waterproofing membrane lacking reinforcement is specified, such use should be approached carefully in-line with third-party certification guidelines as to their suitability for specific projects. 

Selecting a reinforced waterproofing membrane also aids with crack bridging, emphasising its ability to offer protection to the roof structure over the course of its lifetime. Therefore, architects and specifiers can be confident they are specifying a robust system that will meet building regulations and maintain the performance requirements of the roof. 

Another advantage to selecting a reinforced cold-applied liquid membrane is the improved visibility of consistency in relation to the consumption rates, whereby it is much easier to notice any uneven patches of the liquid resin during application. This in effect contributes to a more seamless, aesthetically pleasing finish, also enabling the installer to provide a safe surface for requirements such as enduring foot traffic with the addition of optional anti-slip media. 

The consistency of the membrane achieved through the use of reinforcement is a critical element to its performance. This is due to the fact the substrate surface is never completely smooth in real-world applications, especially in overlay situations. When a liquid is used without reinforcement, run-off will occur from raised sections of a substrate (such as a felt lap joint), creating thinner areas of material as it runs off and pools in lower areas. This in turn creates stress differentials, which can lead to splits and cracks, particularly in the thinner areas.

Risk Management: Selecting a Reinforced Membrane 

Mitigating the risks associated with flat roofing is crucial to achieving a robust, high-performing system that serves the functionality of the building upon which it is installed. Polyroof’s range of advanced liquid roofing systems are fully reinforced to provide long-lasting waterproofing for both refurbishment and new-build applications. Formulated with RapidCure technology for fast and disruption-free installations, our tough and flexible membranes can be specified on roofs of all shapes, sizes, and complexities. 

Take our market-leading Protec Evolve System, for example, where the glass fibre reinforcement layer is applied with the resin basecoat, providing superior durability and performance over alternative, non-reinforced membranes. Complete with BBA certification for a projected lifespan of at least 30 years, the system is ultra-low odour and highly versatile with the ability to form excellent adhesion to a range of surfaces, making it ideal for environments that incur heavy duty foot traffic or require anti-slip solutions. As a carbon neutral product, you can be confident you are specifying a waterproofing membrane that is both sustainable and reinforced for optimum performance.  

For further information about Polyroof’s Protec Evolve System, please get in touch to speak with a member of the team. Further reading on the topic of reinforcements in liquid applied membranes can be found in the Liquid Roofing and Waterproofing Association’s article on their website.


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