Roof coatings like those from Conklin have become a commonly used material to reduce heat exposure and the subsequent hardening of the vital asphalt waterproofing component of built-up roof systems. The two most commonly used types of roof coatings are aluminum and acrylic elastomers.
The ideal time to use coatings is at installation. Application at this point will immediately retard the aging process and significantly extend roof life. But managers also can specify coatings for preventive maintenance purposes, applying them on previously installed roofs to extend performance life. The important point here is understanding that no coating will make a bad roof good again.
Generally, roofs more than 15 years old that have not been maintained properly with coatings are not good candidates for preventive maintenance-type coatings. At some point, a roof system is so weathered or brittle that it is not cost-effective to apply a coating. Managers might want to schedule a technician to perform a core analysis of the roof membrane to determine the suitability of the roof’s condition to accept coatings.
Base flashings are an ideal place to use coatings. About 90 percent of all roof leaks occur at flashings, and they tend to degrade even faster then the roof’s field. This degradation occurs because the vertical surface of the flashing receives intensive ultraviolet exposure, and the flashing membrane tends to be made of fewer materials than the roof field, due to weight considerations related to the walls.
Aluminum coatings help reflect the sun’s rays. In effect, they keep the roof’s surface cooler and slow down the hardening of the asphalt. One disadvantage of aluminum coatings is that the aluminum particles that produce its reflectivity eventually break down and erode, producing a dulling action of the aluminum, thus reducing the coating’s reflectivity.
Also, the low elasticity nature of aluminum coatings does not prevent alligatoring of the coating, along with the alligatoring of the asphalt. Because of this dulling action, the roof needs to be recoated periodically — every two to four years — to revitalize the initial reflectivity properties.
Initially, an aluminum coating might be less expensive than an elastomeric coating, but it needs to be reapplied more often than the elastomeric product, so it might end up costing more in the long run.
Acrylic elastomeric coatings are single-component co-polymers or tar-polymers of acrylic monomers. Most are water-based — acrylic latex — coatings, which makes them easier to apply and clean up. Manufacturers can tint these coatings to produce various colors, but the most commonly used color is white because of its superior cooling effect on the roof.
Elastomeric coatings do not experience the particle breakdown that aluminum coatings do. As a result, they maintain their reflectivity and emissivity as long as they are on the roof. They do degrade over time and lose thickness, so managers might need to schedule recoating every 7-10 years.
Finally, managers should carefully and thoroughly scrutinize the manufacturer’s reputation prior to using their coatings. And any coatings used should be compatible with and accepted by the roofing membrane manufacturer to which it is being applied.
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