By James R. Kirby, RCMA Coatings have been successfully used as part of roof assemblies for more than 50 years in the United States. However, in other parts of the world, coatings have been employed for millennia. The development of sophisticated protective coatings occurred in the latter half of the 17 century, when a German chemist found a way to use the stickiness of coal tar as protection on wo od and ropes. During the 19 and early 20 centuries, scientists developed or discovered various new organic, inorganic, and synthetic materials for use in coatings, binders, and solvents. Perhaps the most dramatic advance in coating properties has come in the past 40 years, with the development of polymers.
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.
Roof coatings are thicker than traditional paint, and have higher solids content; they are also applied in greater volumes. They are formulated to resist weather for many years and are also extremely elastic because they typically contain a level of high-quality resins that are introduced during manufacturing allowing the material to maintain its elastic property. Once cured, these resins form an elastomeric and durable film, which provides an additional measure of waterproofing and allows the roof coating to bridge small cracks and membrane seams . For more on specific kinds of roof coatings, visit constructionspecifier.com