Types of Liquid Membrane Roof Systems

Liquid membrane roofing is a monolithic, liquid-based coating that cures to form a rubber-like, elastomeric waterproof membrane. This lightweight roofing membrane has gained popularity with construction professionals, contractors and architects as an alternative to traditional roofing. Below we will discuss the three most common varieties of liquid membrane roofing systems to help readers identify the best solution for their building type.


Polymethyl methacrylate (PMMA) liquid roofing systems cure remarkably fast and will tolerate a wide range of temperatures during the application phase, including freezing temperatures. It creates a watertight barrier in about an hour and offers waterproofing, UV resistance, and alkali resistance. PMMA coating is durable, flexible, and uses reinforcing fleece that helps reduce cracking and increase the lifespan of the material.

PMMA roofing systems are relatively easy to apply. The liquid material spreads an even coating on the roofing surface, filling every void, gap, and crack. The PMMA layer creates a strong and waterproof bond on virtually any standard roofing substrate and also works with variable substrates when used in conjunction with the right primer. PMMA offers fast overcoating with sealer coats and topcoats. These properties make PMMA an ideal choice for many repair projects.

PMMA liquid membrane roof systems resist water pooling and feature good resistance to chemical corrosion. The material has low volatile organic compound (VOC) content, making it safe for use in sensitive environments such as healthcare facilities.


Polyurethane is much like PMMA but has  a low solvent odor. Polyurethane liquid roofing systems apply seamlessly, filling gaps as large as 2mm. The material becomes water-resistant quickly and cures in only 24 hours. Polyurethane bonds well with a range of roofing materials, including  asphalt, single ply, bitumen, fiber cement sheets, and concrete. When used with an additional topcoat and a non-slip aggregate such as granules or sand, the material’s waterproofing properties remain even under regular medium-to-heavy foot traffic.

Polyurethane liquid membrane roof systems are low-maintenance and are receptive to quick patching or repairs when damaged. Roofing application is quick and efficient using sprayers and rollers.  Despite a low overall cost, polyurethane features long-lasting service life. The surface reflects sunlight, contributing to low thermal conductivity. It is also resistant to common chemicals, oils, and detergents.


When looking for a quick and easy solution that handles extreme temperatures and weather conditions, silicone may be the ideal option. Liquid roofing systems with silicone are inexpensive and durable. Silicone creates a smooth surface that is watertight and resists pooling water. It will not crack or become chalky, and will resist UV rays, mold, stains, and mildew. Silicone does not soften in water, withstands extreme temperatures, and maintains dimensional stability.

Silicone liquid membrane roof systems can renew materials to extend the overall roofing lifespan. Silicone bonds well to concrete, polyurethane foam, wood, single ply, mineral cap sheet, and metal roofs without primer. This liquid membrane is best for flat roofs and roofs with a low slope. It even works on weathered roofs and can cover gaps filled with tape or polyester mesh.

Liquid Membrane Roof Systems From Knickerbocker Roofing & Paving Co., Inc.

Each variety of liquid membrane enhances the waterproofing and durability of traditional roofing systems. Knickerbocker Roofing has been satisfying roofing customers since 1886 and remains family-owned. Our roofing specialists can help you find an ideal solution. Contact us or request a quote for assistance selecting the best liquid membrane roofing system for your structure.

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