IS YOUR ROOF A CANDIDATE FOR SILICONE ROOFING?
While silicone is a very effective roofing system and can adhere to just about any existing roof, there are certain exceptions. There are situations where adhesion may be in question and a primer may be needed. These are rare and aren’t something to worry about, but they are something that you should be aware of. Let’s look at various roof types and see when you might need a primer. As a general disclaimer, we recommend that every roofing project is preempted with an adhesion test. This test will ensure that silicone adheres to your roof, or will let you know that you might need a primer.
Roofs that Never Need a Primer
“Never” is a strong word, and might be an exaggeration in this case. There will almost certainly be an exception sometime, somewhere and one of these roofing systems will need a primer, but we haven’t run into it yet.
Concrete
Silicone Coated
Skylights
In our experience, these three roofing systems don’t need a primer for adhesion, they don’t need a primer to prevent bleeding, or anything else that primers are designed for. If your roof is one of these three types, you can almost surely apply a silicone coating with no concern of primers.
Roofs that Might Need a Primer, but Not for Adhesion
Beyond the first list, there are also some roofs that might need a primer, but it isn’t for adhesion. Certain roof systems can adversely impact the appearance of silicone. While the roof will still adhere fine, it won’t look great.
Aged Asphalt
Granulated Cap Sheet
Gravel BUR
Modified Bitumen
Smooth BUR
Each of these roofs contains chemicals that remain in the membrane long after installation. Once the coating is applied, these chemicals can actually leach out of the membrane and into the silicone. This causes a yellowing of the coating that is unsightly to some, while others don’t mind it. If you don’t mind the yellowing or if your roof is out of sight, then no primer is required. If, however, you want a bright white roof (who wouldn’t), then a bleed-block primer will give you just that. You don’t have to have the primer, but you can choose to use it.
There are a few other roofing systems that may require a primer, but not for adhesion. Let’s look at these below.
Metal – If the roof is rusted, a rust inhibitor is recommended to stop the spread of rust.
SPF – A primer is occasionally used to improve the yield of the coating (to get more square footage out of each gallon).
Roofs That Might Need a Primer for Adhesion
There are also some roofs that occasionally do need a primer for adhesion. They don’t always require a primer, but if they do, it’s because the silicone won’t adhere to the roof without one.
Campers/RVs
Hypalon
PVC
TPO
These roofs are all single-ply membranes that often have an oily film on them at installation. This oily film prevents the silicone from getting a good hold on the roof itself. As the oil comes off the roof, the silicone will too. So, we offer a primer that cleans off this oily film and allows the silicone to adhere perfectly. One thing to note about single-ply roofs: the oil usually disappears within five years. If your roof is older than five years, you most likely DO NOT need a primer. We still, of course, recommend an adhesion test just to be sure.
Roofs that Require a Primer for Adhesion
Finally, which roofs require a primer to allow silicone adhesion? Which roofs have we discovered that you must have a primer before installing a silicone coating?
EPDM
That’s it, that’s the list. After all the roofs we’ve installed coating on, EPDM is the only one that we’ve found to require a primer. That’s pretty good, right? EPDM, like single-ply, has a film on top of it after installation. This is a thin black film that doesn’t go away on its own. If you walk on an EPDM roof, your shoes will actually become black from this film. The primer we recommend is actually rinseable. You spray it on the roof and then powerwash it off about 15 minutes later. This clears off the black film and preps the roof for silicone installation.
Conclusion
So there you have it. 3 roofs never require primer, 5 roofs might require primer for aesthetic reasons, 2 roofs might require primer for non-adhesion reasons, 4 roofs might need a primer for adhesion, and 1 roof type does need a primer. Those are pretty good numbers if you ask us. If you have one of these roof types and would like an adhesion test, head on over to our shop and order one. We’ll ship it out immediately to see if your roof is a good fit for silicone.
