Roof coatings became popular in the 1970’s and 80’s, along with the “Bee Gees”, and they have been around ever since. Coatings are applied over an existing hot tar roof in an effort to “extend” the life of the roof and to add reflective qualities to the system. This is sound thinking, however, in many cases, coatings are misrepresented by the coating industry and contractors who install them. Most of the waterproofing is done before the coating is even applied. (All cracks and holes are mended with plastic roof cement.)
To “extend” the life of the roof could mean getting an extra year or two out of the existing system. But I have heard boasts of 10 and 15 year warranties that may not hold water. I installed one of these coatings exactly as directed by the manufacturer. After being told that I would get a 10 year “leak free” warranty from the manufacturer, I had to refund my customer’s money after the first year. I then installed a single-ply TPO system to keep water out of the building and to keep myself out of the “People’s Court.”
Since elastomeric coatings are as thin as a piece of paper, how could they be expected to maintain a waterproof membrane for more than a year or so? They can’t and they don’t.
Coatings are not to be confused with actual roofing systems like hot tar, torch-down or single ply. Coatings, by themselves, are not considered to be a legitimate roofing system. They are considered to be a roof restoration only.
Coatings are often required to be installed over a cap-sheet roof so it meets the Title 24 (Environmental Reflective Demands) requirement. But it was never intended as a waterproofing system in itself. Single ply systems, on the other hand, have a reflective coating, that meets Title 24, built right into the system.
The best available flat roofing systems as of January 2015 are single-ply systems (TPO or PVC) that carry 20-30 year warranties. Hot tar systems are legitimate, but they do not compare with the single ply across the board in terms of safety, longevity, environmental issues. Torch-down is at the low end of the tier. It has the shortest lifespan, uses open flames, and has safety issues.
Emulsion and elastomeric coatings rely on the roof system that they are covering for longevity. When the roofing that the coating is covering deteriorates, then the coating fails.
I know of some manufacturers offering 10 year warranties on their coatings however, the warranty has stipulations that do not protect the property owner. The cost of coatings is about half of regular flat roofing options so many property owners are lured by the lower prices and the long warranties, however these warranties do not stand up to close scrutiny.
Single-ply roofing does not rely on the existing roofing at all. It stands by itself, whether it’s over an existing roof or bare plywood. It is like large sheets of thick rubber. This material is substantial and will not allow water to penetrate it for 20+ years. The warranties for single-ply are legitimate and are validated by reputable companies.
There is really no comparison between the two. One is akin to painting over a roof (coatings) while the other is a new roof covering (single-ply).
New buildings across America are roofing with single-ply roofing. No building chain (Lowes, Home Depot, WalMart etc.) is roofing their buildings with a coating only.
Hot tar roofing is an acceptable re-roofing choice as it is substantial and will last 15+ years; however single-ply is the better choice for longevity, reflectivity, and environmental effects. (No fumes, not oil based, and it’s recyclable.)
Tom Scherer is with T and G Roofing and can be reached at (818) 459-0702 or www.tandgroofing.com.