The Proper Steps to Cover Aluminum Roofs with White Roof Coating

Paint-on Coatings

• Paint-on roof coatings provide a seamless environmental barrier, making them an ideal first layer of defense against precipitation and wind-borne atmospheric contamination. When factory-applied coatings degrade, as they do relatively quickly when exposed to extremes of temperature, a new coating can extend the roof’s working life considerably. Such coatings also reduce the leak potential of screw holes and penetrations for appliance vents. Low-thickness, high-performance membranes offer a balance of results with ease of application.

White Roof Coatings

• White roof coating is acrylic or elastomeric, meaning it is made from a nonbituminous base. The Roof Coatings Manufacturers Association describes the products as “a polymeric binder blended with pigments.” The Cool Roof Rating Council recommends white coatings above any other "cool color": They have the highest reflectivity, meaning they bounce back more of the sun’s energy than any other color, and the best emissivity -- the amount of heat emitted after conversion of infrared and ultraviolet energy into heat. Reducing the heat that penetrates the building equates to reduced cooling costs. Reflectivity also reduces “thermal shock,” the phenomena of roofing materials having a conspicuously shortened life span caused by the expansion-contraction cycles of frequent, extreme changes in temperature.

Preparation

• The aluminum roof must be scrupulously clean before application. Observe all the coating manufacturer’s directions. Typically, the entire area you wish to coat should first be swept or blown off, thoroughly pressure-washed with a dilute detergent and rinsed. Some products require applying a proprietary degreasant followed by a second thorough rinse. After this procedure, allow the roof to dry.

Physical Considerations

• Inspect the roof for soundness; address structural problems, such as lifting screws, torn corners, uneven seams and buckled aluminum panels, before coating. Replace any missing fasteners. You may need to remove pre-existing coatings entirely -- overspread of cement and seam sealers certainly should be removed. If so directed, apply a brush- or roll-on flashing sealant over fasteners, penetrations -- for example, flues, vents and air conditioner ducting -- and seams. Most white roof coatings require you to apply a primer first; follow the manufacturer’s directions precisely. Up to three coatings may be necessary to achieve the optimum thickness.