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Wear I've Not Seen Before

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It's a glass mat isolation membrane that's being used as a cover. The cheap SOB's way of putting on a low-pitch cover and even when new with a fresh coating of asphalt is a piece of crap that has an expected service life (according to Jorve roofing) of about 7 years, tops.

It'll probably be worn out before the ink on your report is dry.



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Interesting. Derbigum. I've never been able to find the name of that stuff.

There were a number of these installed on large apt. buildings in Chicago in the late '70's, mid-80's, invariably by slumlord creeps and condo conversion weasels.

If you lean on them, you get more glass fibers in your hands and forearms than you can imagine. I hate the stuff, but if it's kept coated, it can keep the water out.

POS stuff, though.

Chris, do you have your own shop, or work for someone (Sheriff-Goslin)?

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Derbigum is (or at least was) considered a "premium" mod bit. I've toured their plant and it's pretty cool to see how that stuff is made.

An earlier version of their product had a polyester/fiberglass scrim laid in the top third of the sheet and we used to see it coming through all the time. They always said it was normal and not an issue, and I don't remember ever observing a leaking condition due to the sheet. It does look sick as hell though.

When I first saw Randy's photos that was the first thing I thought. Derbigum. But photo 3 looks more like a thinner base ply sheet, and not a mod bit, to me.

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It's exactly what I said it was. I know, 'cuz I see the stuff all the time. It's roughly 1/40th of an inch thick. They usually lay down some mastic, roll this stuff out into the mastic and swab on a thin layer of mastic and call it a day. Like I said, one of the most reputable roofing companies around here says that it'll last 7 years if they're real lucky.

OT - OF!!!


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First photo looked like Derbi-Gum we were applying in the mid to late 70's at Hans Rosenow Roofing in Chicago.

Then, the other shots showed it was a fiberglass felt applied with either hot tar, but probably more likely and adhesive mastic with a squeegee (sp).

Wrong material for the job.

Vertical seams on a properly installed Built Up Roof is an acceptable manner of application.

Also, look at all of those Polish Bungalows in Chicago with 90# Roll Roofing face nailed on the seams installed vertically.


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