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Recoating flat asphalt rolled roofs


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A question for you roofing guys:

I often run across flat rolled asphalt roofs that have been coated with a silver-ish sealant. Often times, the sealant is cracking in places. At what point in the 'cracking process' would it be prudent to recommend recoating the roof? Typically, when I see the cracking, I note it and recommend recoating at least the cracked areas (if only some areas show this wear).

Also, is there a limit to how many times a roof of this sort can be recoated? Sometimes I can tell several layers of this sealant have been applied. At which point, for this type of roof that has been repeated recoated, should the entire roof be replaced?

See the attached photo.

Up to this point, I've made pretty conservative recommendations for CYA. Just curious if I am making the right recommendations.


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Matthew -

Can't see the photo but I'll assume you are talking about modified bitumen.

The standard silver coating that most of us will come across in a residential inspection is a plain old non-fibrated UV coating, sometimes referred to as a silver coating. It has absolutely NO waterproofing abilities. It's purpose is to protect the membrane from the UV rays which breakdown the roofing materials.

Proper application requires that new roofing material is cured (installed 30 or more days ago) and here's the rub....clean. Not broom clean, but washed from all the dirt that accumulates over 30+ days. So 99.999% of the time it is installed incorrectly and will not last as long as it should, which is about 5 years. If ponding is present it will erode even quicker.

An approved UV coating will extend the manufacturer's warranty by 2 years (at least for mod bit), which should translate into more than 2 years of extended life.

Recoat when you can see the surface. Cracking or crazing is not a big deal.

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Cary, thanks for the feedback. Yep, I am talking about modified bitumen. So, recommending at least touchup where cracks are visible isn't really needed? If the silver coating has no waterproofing properties, then I would think if a large number of cracks are visible, leakage is more common/possible.

How many times can this sealant be applied over itself? In other words, is there a limit to when replacing the roof is needed instead of just applying another coating?



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That's a hot tar roof - usually 2-3 plys of felt topped with a flood coat. They need recoating with hot tar regularly and still barely make it to 15 years. The silver coat just reduces UV.

That pic shows deep alligatoring of the flood coat. Nobody's doing hot coatings anymore. I haven't been stuck driving behind a smelly kettle for at least ten years. Your clients aren't likely to find someone to recoat, even if it qualifies for another coating. I usually tell folks it's time for mod bit or rubber.

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Originally posted by msteger

It was definitely built-up/modified bitumen, but I did notice a perimeter piece installed, not common for what I see with most exposed (uncoated) bitumen. This sort of perimeter piece is what we normally see on rubber membrane roofs.

Matthew, a built up roof and a modified bitumen roof are two different things. The roof in your picture sure looks like a built up roof, made from alternating layers of roofing felt and asphalt (or coal tar). The cracking in the picture is limited to the final puddle of asphalt. It's a very, very common phenomenon, practically universal on built up roofs. There are always excess puddles on asphalt here & there. The cracks in that picture really don't signify.

Modified bitumen roofs are made of rolls of roofing that are applied with a torch or with a cold process adhesive. They look nothing like the roof in your picture.

Rubber roofs are EPDM and are not the same as modified bitumen.

- Jim Katen, Oregon

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  • 3 weeks later...

It is a Built Up Roof.

The cracks are from the mopping excess when the wall flashing composition flashings were hung, as you see the thicker mass coincide horizontally along the bottom edge of the wall flashing material.

Too much asphalt, such as when the mop yarn gets squeezed dry to hang for the evening will leave puddles, which will quickly crack due to being an unreinforced Blob of asphalt.

The Aluminum coating is still in good shape and it is Not the coating that is cracking, but the excessive flow of asphalt that it is adhered to.

I did not see a good view of the entire roof surface to see how many plies it was, but I saw No evidence of any Modified Bitumen installed, unless they used some for some flashings I did not see.


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