The recent article "Roof coatings: for better or worse" by Dick Baxter, president of CRS Inc., Monroe, N.C., in the May issue, page 50, prompted my letter.
Although the Reflective Roof Coatings Institute (RRCI) is aware of Baxter's frequent contributions to Professional Roofing, it is clear he is not well-versed in some key aspects of roof coatings.
To his credit, Baxter makes a key point about the need for evaluating a roof's condition and proper surface preparation before coating application. As roof coating manufacturers, RRCI members insist on proper surface preparation and note a primer is not a substitute for cleaning. In his summary, Baxter notes the need to understand the quality aspects of roof coatings and performance benefits they create.
Now for points where Baxter falls short:
On balance, Baxter makes a few worthwhile points, but on key technical aspects that move the subjective discussion to objectivity, he overlooks industry-accepted methods already in place.
William A. Kirn RRC
Kansas City, Mo.
Following is Baxter's response to the article:
My article was directed to contractors to call attention to some pitfalls surrounding the use of roof coatings. It describes methods any contractor can use to evaluate different coatings he intends to use on any given project.
I'm not personally an advocate of ASTM International. Most ASTM specifications are manufacturer-oriented, generally describe the lowest common acceptable properties, provide no qualitative information and are used more as a "cover your ass" method by marginal suppliers when their stuff doesn't work.
Whether Kirn questions my test methods, they provide quick indicators of the properties of various coatings for comparison. Most methods I use can be used by any roofing contractor to compare prospective coatings without involving a testing agency that only would test to an ASTM specification and generally provide no useful information.
Regarding drying time: It is absolute fact as raised by Kirn that ambient conditions will dictate the length of time a coating takes to "skin." But when all coatings to be compared are set side by side in a perfect environment and drying time, or skin time, is dramatically different from coating to coating, I'll pick the quick skin every time.
I assure Kirn that when a surface is properly prepared and a coating has good adhesion properties, the woven glass fabric will tear out before the coating releases from a properly prepared surface/substrate. Along the same vein, my experience also is that a properly prepared and formed taped seam in EPDM roof membranes will hold as the EPDM tears around the seam.
I never said there were no suitable coatings for TPO, APP-modified asphalt roof membranes or prefinished steel. I only said special primers and perhaps some special surface preparation may be required to get the coatings to bond.
As for reflectivity, all white surfacesincluding white coated surfacesbecome dirty over time and lose their reflective properties. I don't recall having said white coatings would not adequately cover dark surfaces though some lesser-quality coatings may require multiple applications to completely hide dark surfaces.
The simple fact is coating properties vary significantlyeven products from the same supplier. Some are better suited for roof system applications than others, but I wouldn't rely on an ASTM specification to tell me which ones!