Roof coatings are designed to protect and extend the service life of roof assemblies for new construction and, more commonly, for existing coverings, such as built-up (BURs), metal, modified-bitumen (mod-bit), single-ply, and sprayed polyurethane foam (SPF) systems. Coatings protect roof membranes from ultraviolet (UV) degradation and weathering, assist and enhance a system’s fire resistance, and provide a watertight layer on an existing roof. These coatings can enhance reflectivity and improve the aesthetics of the surface, lessening the building’s cooling load and heat island effect because the heat strain on the roof has reduced. Roof coatings also help decrease expansion and contraction of the membrane, by minimizing the membrane’s temperature swings. The most common types of roof coatings are acrylic, polyurethane, and silicone.
Acrylic water-based coatings are suitable for high UV environments where a reflective roof is desired. They can be colored, but generally are sold in white, tan, and grey. Many specialized versions are compatible with specific substrates.
Polyurethane coatings are typically solvent-based and come in two main types: aromatic (less UV-stable) and aliphatic (very UV-stable). Urethanes have good mechanical properties and high abrasion resistance. They are best used in hail-prone regions and where a roof is exposed to heavy foot traffic.
Silicone coatings, like acrylics, are suitable for high-UV environments where a reflective roof is desired. Silicone is often used in locations where rain is a daily occurrence, or if the roof is often wet and experiences a lot of ponded water.