This article was posted on Sunday, Mar 01, 2015

Roof coatings became popular in the 1970’s and 80’s, along with the “Bee Gees” and 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 the contractors who install them. Most of the waterproofing comes before the coating is applied. All cracks and holes are mended with plastic roof cement. This is what any roofer would do as part of a repair or to simply maintain the roof. The coating is applied mainly to meet the standards of a cool roof. 

“Extending” the life of the roof, as the coating industry claims, could mean getting only an extra year or two out of the existing system. But I have heard boasts of 15 years and 10 year warranties. I actually installed one of these systems exactly how the manufacturer directed me, after being promised how great the coating was and that I would get a 10 year “leak free” warranty from the manufacturer of the coating. Instead of being “leak free”, I had to refund the customer’s money after the first year and install a single ply TPO system to keep water out of the building and to keep me out of the “Peoples 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.  Most people who fall prey to empty promises find that they have to reapply the coating every couple of years. This greatly reduces the return on their investment, leaving the property owner’s pockets as empty as the promises made to them by the coating supplier. 

Coatings are not to be confused with actual roofing system like hot tar, torch-down or single ply systems. Coatings, by themselves, are not considered a legitimate roofing system, only an additive to an existing roof system. Coatings are often required to be installed over a cap-sheet roof so it meets Title 24 (environmental reflective demands) requirements. But it is not a waterproofing system in itself.

Single ply systems, on the other hand, have a coating that is built into the material and they do not need anything additional for reflective qualities. They did it this way before it became a requirement. These systems have been around for a long time and there have been many improvements made over the years, which is why they are so widely used in the new construction industry today. Single ply roofing systems (TPO or PVC) are simply the best available roofing system to date. They carry a 20 to 30 year warranty.

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Hot tar systems are legitimate, however they do not compare with the single ply across the board. Hot tar has safety, longevity and environmental issues. Torch-down is at the low end of the tier with the shortest lifespan, open flames, and other safety issues. Emulsion and elastomeric coatings don’t even make the tier as they rely on the roof system that they are covering for longevity. When the underlying roof system fails, the coating fails. So if you need a new roof, do not coat your old decaying roof with liquid paint. You will need a new roof within a couple of years. The bottom line is, coat your roof if you want it cooler in your dwelling but if you need to keep the rain out you will need a roof system not a coat of paint.  

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 over an existing roof or over bare plywood. (It is like large sheets of thick rubber) This material is substantial and will not allow water to penetrate for 20+ years. The warranties for single ply are legitimate and valid 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). 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. There are no fumes and it is recyclable.

New buildings across America are roofing with single ply roofing. These are reputable companies who research before they build. There is not a single chain of buildings (Lowes, Home Depot, WalMart etc.) who roof their buildings with a coating only. It simply can’t be done.  

Tom Scherer is with T&G Roofing and may be reached at (818) 459-0702 or by visiting