The importance of reinforcement in cold-applied liquid roofing

We’re delighted to welcome Sarah Spink as our guest blogger. Sarah, CEO of the Liquid Roofing and Waterproofing Association (LRWA), explains the importance of reinforcement in cold-applied liquid roofing.  

Cold-applied liquid waterproofing, commonly used in refurbishment projects, is often applied over existing roofing systems. Reinforcement increases the tensile strength of the liquid waterproofing, thereby reducing its elasticity.

Navigating the wide variety of liquid waterproofing systems can be daunting, often leaving specifiers and contractors uncertain about the best choice for their project. The LRWA has seen firsthand the negative outcomes when projects use unsuitable products.

Typically, a liquid-applied membrane with reinforcement should be the standard choice when selecting a system. While there are exceptions, which we’ll detail below, reinforcement significantly reduces the risk of system failure.

Avoiding mistakes

Although some products without reinforcement may promise exceptional durability, it’s crucial to verify their suitability for specific substrates. The easiest and most reliable method is to check third-party accreditations like the British Board of Agrément (BBA), European Technical Approvals (ETA), or BDA certificates.

To assist specifiers in evaluating liquid roofing products and minimizing risks, the LRWA has created specialist guidance and tools. One such tool, the Liquid Roofing Finder, is a free online resource that uses third-party accreditation to help specifiers, distributors, and contractors quickly assess the suitability of various liquid roofing systems and their approved substrates.

Essential reinforcement

The LRWA has observed some manufacturers introducing liquid systems to the UK market without a reinforcement layer. These products, often promoted for their cost-effectiveness and quick installation, are primarily available through merchants.

Cold-applied liquid waterproofing, often used in refurbishment projects, is usually applied over existing roofing systems. Reinforcement boosts the tensile strength of the liquid waterproofing and reduces material elasticity. Reinforcement layers, typically made from polyester fleece or glass fibre mat, allow for greater thermal or structural movement in the substrate, thereby reducing stress in the membrane at movement points. When properly applied, the strength of the reinforcement exceeds the bond to the substrate, permitting greater movement and preventing membrane damage.

Reinforcement is especially vital in high-stress areas like upstands, movement cracks, and expansion joints. It also aids in bridging cracks, especially if they appear after the membrane application in a roof or balcony substrate. A fully reinforced system has much greater overall strength than liquid resin alone, offering increased flexibility around cracks and reducing potential issues.

Installation factors

Using an unreinforced system can lead to increased stress instead of elongation, potentially compromising the system’s durability and integrity. This risk persists even if no cracks are present during installation, as no liquid-applied resin alone can provide infinite capabilities.

Contractors should be aware that some liquid waterproofing systems without reinforcement recommend using reinforcing strips over cracks, joints, or stress points to improve performance in critical areas. However, this approach increases project costs without providing a comprehensive, seamless reinforced system.

Reinforcement also ensures consistent thickness of the waterproofing membrane, which is crucial for withstanding foot traffic and varying weather conditions in the UK’s diverse climate.

Exceptions

Some liquid-applied waterproofing membranes do not require reinforcement, particularly those that cure extremely quickly and are typically approved for use on concrete in new-build projects. Additionally, liquid-applied membranes used on materials like metal profiled or asbestos cement sheets may need partial reinforcement in areas prone to movement. In these cases, specifiers and contractors should consult the manufacturer’s guidelines regarding the substrates tested with partially or non-reinforced systems.

At CRS, we are experienced in applying all types of cold-applied liquid roof systems and can advise on the most suitable solution to meet your requirements. Get in touch with our team if you’d like to discuss liquid roofing solutions.