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Dennis Davidson Posted: Jul 11, 2009 09:06 AM	25+ year old foam roof with new blisters Mason I have a existing foam/urethane roof that is over 25 years old. I did not install this one but I have applied two urethane re-coats on it. I noticed new "foam" blisters occurring last year and even more new one this year. The building is a one story wing of a school (class rooms) with a metal deck, 1/2" fiber board stock, 1 1'2" foam and about 50+ mils of urethane coating. There are about 30 - 6" foam (3/4" thick) blisters over 18,000 sq ft and there seams to be more over the hallways than classrooms. Yesterday I went inside and noticed the ceiling tiles were all bowed and the tracks had some rust starting. I found out that over the past few years, that all windows and doors are kept closed all Summer with the a/c going while they mop and wax the floors. (high humidity) I've worked on building in the South that are kept closed year round that didn't have this problem. I took a core down to the metal deck and it was completely dry. Any thoughts?
mason Posted: Jul 11, 2009 02:11 PM	I had that happen to me on a 20 + year old foam roof. When we put a primer on the old coating, blisters appeared almost immediately. We discovered that the foam had marginal interlaminar adhesion that didn't become a blister until we put a darker coating over the foam. That darker color made the foam a higher temperature and caused it to expand just enough to cause the blisters. I don't know if that is the situation in your case but it is something to think about. Was the urethane coating a darker color? If the base coat was dark, it might have expanded the foam enough to cause blisters later on.
mason Posted: Jul 11, 2009 02:18 PM	Another thing, old foam roofs can have new blisters if the interlaminar adhesion is not as good as it should be just from the building movement and thermal shock.
Dennis Davidson Posted: Jul 11, 2009 03:02 PM	Interesting thoughts. When I originally re-coated this roof, I did use a black primer and a light gray coating, but that was a long time ago. The current color is aluminum put on 3 years ago. I think your right with the loss of adhesion between layers of foam. This area has experienced higher that normal Summer temps. for about the last three years. Even breaking some heat records. So, weak areas were finally pushed to the breaking point. Makes sense! Thank's These roofs have served well past the expected life. Maybe it's time for a scarrf and re-foam to make it last another 25 years.

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Dennis Davidson

Posted: Jul 11, 2009 09:06 AM

25+ year old foam roof with new blisters

Mason

I have a existing foam/urethane roof that is over 25 years old. I did not install this one but I have applied two urethane re-coats on it.
I noticed new "foam" blisters occurring last year and even more new one this year.
The building is a one story wing of a school (class rooms) with a metal deck, 1/2" fiber board stock, 1 1'2" foam and about 50+ mils of urethane coating. There are about 30 - 6" foam (3/4" thick) blisters over 18,000 sq ft and there seams to be more over the hallways than classrooms. Yesterday I went inside and noticed the ceiling tiles were all bowed and the tracks had some rust starting. I found out that over the past few years, that all windows and doors are kept closed all Summer with the a/c going while they mop and wax the floors. (high humidity)
I've worked on building in the South that are kept closed year round that didn't have this problem.
I took a core down to the metal deck and it was completely dry.
Any thoughts?

mason

Posted: Jul 11, 2009 02:11 PM

I had that happen to me on a 20 + year old foam roof. When we put a primer on the old coating, blisters appeared almost immediately. We discovered that the foam had marginal interlaminar adhesion that didn't become a blister until we put a darker coating over the foam. That darker color made the foam a higher temperature and caused it to expand just enough to cause the blisters.

I don't know if that is the situation in your case but it is something to think about. Was the urethane coating a darker color? If the base coat was dark, it might have expanded the foam enough to cause blisters later on.

mason

Posted: Jul 11, 2009 02:18 PM

Another thing, old foam roofs can have new blisters if the interlaminar adhesion is not as good as it should be just from the building movement and thermal shock.

Dennis Davidson

Posted: Jul 11, 2009 03:02 PM

Interesting thoughts.
When I originally re-coated this roof, I did use a black primer and a light gray coating, but that was a long time ago. The current color is aluminum put on 3 years ago.
I think your right with the loss of adhesion between layers of foam. This area has experienced higher that normal Summer temps. for about the last three years. Even breaking some heat records. So, weak areas were finally pushed to the breaking point.
Makes sense! Thank's

These roofs have served well past the expected life. Maybe it's time for a scarrf and re-foam to make it last another 25 years.

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