In addition to beauty and waterproofing, roof coatings can add a reflective surface, which works to reduce air-conditioning load on temperature-controlled storage units. Whatever the reason you choose to add a roof coating, the solution can be extremely economical compared to removing and replacing a roof substrate. So which coating do you choose for your facility?
There are four basic roof coatings: asphaltic-based fibrated black, asphaltic-based fibrated aluminum, acrylic elastomeric and urethane. But not all coatings work for all existing roof substrates. In fact, for metal roofs, an acrylic or aluminum-asphaltic coating may be the most economical choice. A urethane could be used, but the benefits of this coating on metal are minimal compared to the additional cost. So when selecting a roof coating, consider your roofing substrate and your needs.
Asphaltic-Based Fibrated Black Coatings
Black asphalt-based fibrated coatings are used mainly as an economical waterproofing coating for smooth built-up or modified bitumen roof systems. These types of coatings are available in solvent- or water-based formulas and require the addition of aggregate for UV protection or a reflective coating (such as an aluminum) for energy efficiency. Of course, this extra step of adding an aggregate or reflective coating may just make this economical choice more costly.
Asphalt-based black coatings have been used to patch metal-roof substrates, but in addition to the unsightly look of the black coating on metal, the coating, if it does not have enough elasticity, may crack when the roof expands through its heat and cool cycles. For built-up and modified bitumen roofs, expect the coating to provide an additional three to 10 years of service life.
Asphaltic-Based Fibrated Aluminum Coatings
Aluminum coatings, which are typically asphalt-based products, are often used to add reflectivity to a built-up or modified bitumen roof surface or to rust- and waterproof metal roofs. The quality of the asphalt in the product provides the waterproofing and rustproofing layer and stops tight rust from continued corrosion on metal roofs. With the addition of high-grade aluminum flake to the asphalt, the aluminum protects the asphalt from UV rays, providing for longer protection. A quality aluminum coating should not require priming, reducing the overall installation costs.
Aluminum coatings are best for treating rust and preventing it from spreading. While the only color choice for this coating is aluminum, the aluminum appearance can give an unattractive rusted roof a more pleasing image. In addition, the aluminum naturally protects the asphalt in the coating from UV radiation and provides 50 percent to 65 percent reflectivity. One further benefit to aluminum coatings is they are not limited to low-slope applications and can be used for steep slopes. Expect a good quality, fibrated aluminum coating to protect from five to 12 years.
When color is important, an acrylic- elastomeric coating is ideal for most roof substrates including metal, concrete, smooth built-up, modified bitumen, foam and single-ply roofs. For metal roofs, an acrylic coating requires a primer on rusted areas for proper adhesion. Acrylics can be tinted for a colored roof, although dark colors tend to fade quickly. Also, some manufacturers require primers for most roof surfaces for proper adhesion. With a white coating, the roof surface can reflect up to 80 percent to 90 percent of UV rays; however, when a color tint is added to the coating, the reflectivity level may be compromised.
Acrylic-elastomeric coatings are available in fibrated and nonfibrated formulas. The difference between the two is in the film build (thickness). The fibrated reinforced formulas allow for thicker film builds when applying the product, allowing for a one-coat application. Nonfibrated acrylics have greater elongation than fibrated formulas, but usually take two coats to build up proper coating thickness. A fibrated coating is a less labor-intensive application and is the most economical option when applying an acrylic-elastomeric coating. These coatings are water-based and last an average of seven to 12 years.
Urethane offers a service life of eight to 12 years, the longest of any of the coating options. This solvent-based polymer coating is the most expensive of the four types and offers similar reflectivity to that of a white acrylic coating. Urethanes are resistant to many rooftop chemicals and pollutant exposure and make sense for roofs that are exposed to harsh industrial conditions.
Typically used on built-up, weathered single-ply and foam roofs, urethane coatings can be applied directly to concrete decks and are not limited to low-slope. While the coating can be used on metal roofs, the additional benefit compared to the additional cost of the urethane coating doesn't merit its use.
Selecting a quality applicator, starting with a restorable roof system and warranties are some other considerations when deciding if a roof-restoration coating will work for your facility. Many roofing contractors and some painting contractors provide application services for roof coatings. The quality of the work will determine the length of service, plus many manufacturers require contractors to register with them prior to issuing any warranties.
The key to a long-lasting roof-restoration system is the quality of the roof substrate, which must be in a salvageable condition before coating the roof. A roofing contractor or consultant, or a coatings manufacturer's representative can determine if a roof-restoration coating makes sense for your roof.
Another consideration, especially when deciding which manufacturer's brand to choose, is the warranty option. Warranties are not new to the roofing industry and many manufacturers have added warranty options for roof coatings. Warranties are typically available for a minimal fee per square foot for labor and material. They can provide coverage from two to 12 years, depending on the substrate, the coating and the manufacturer.
Roof coatings not only add aesthetics, but also provide waterproofing, reflectivity and service life (sometimes considerable service life) to a roof. When selecting a coating, consider the existing substrate and conditions, performance expectations, and budget before determining which coating system is best suited to meet your requirements.
Valerie Wolford is marketing manager for Republic Powdered Metals Inc., a Beachwood, Ohio-based manufacturer of roof coatings since 1947. Visit Republic Powdered Metals' website at www.rpmrepublic.com.