Compatibility of Concrete Patching Compounds and Liquid-Applied Waterproofing Membranes – The WSRCA’s Waterproofing Committee Report In Brief
The Western States Roofing Contractors Association’s most recently published bulletin on the compatibility of concrete patching compounds and liquid-applied waterproofing membranes details reports from the field on adhesion problems and other issues with concrete. It describes some of the more common issues broadly encountered, such as excess moisture remaining in the cementitious repair material at the time of liquid-applied waterproofing installation. Under heat, the moisture becomes trapped under the membrane, causing voids and blisters which separates the membrane from the substrate. Compromised membrane adhesion enables moisture migration, further exacerbating the disbonding process. Additionally, if the concrete sealer or primer is not fully cured at the time of the topcoating, the membrane and/or its adhesive may not bond properly and allow moisture to become trapped underneath. On the other hand, the GreenSlope roof leveling compound is designedly breathable and will allow excess water to evaporate easily before being topcoated, speeding up the curation process and allowing for installation and topcoating same day in most cases depending on the temperature and thickness of the application.
Another major concern affecting adhesion between cement fillers and liquid topcoats is cement’s often rugged surface texture when improperly prepared (which is common) – raised fins, divots and chips which causes the membrane to bridge over and leave voids which worsen the adhesion problem. This allows moisture to migrate laterally and causes further disbonding/degradation in areas where moisture is trapped, especially during freeze/thaw cycles. In contrast, GreenSlope is comprised primarily of fine-grained EPDM (ethylene propylene diene terpolymer) and beaded EPS (expanded polystyrene) — materials soft and pliable on the surface but extremely durable when cured. It smooths over easily and leaves a flexible, rubber-like membrane when cured. This malleability and smooth surface texture makes it highly compatible with the vast majority of commonly used liquid-applied waterproofing membranes.
As the WSRCA demonstrates in seven full length pages in their latest report, concrete patching materials can present numerous complications, requiring extensive compatibility confirmation with the waterproof membranes, long durations set aside for proper primer curation on the concrete patching materials, and exceeding care taken during all stages of installation. Given all these complications and the potential for costly repairs down the road, save yourself the hassle and fix flat roof ponding with eco-friendly GreenSlope today.