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Hey Jim,

No issues on that roof. The director of the home stated it was installed approx 7-8 yrs ago. The drains were clear and no seams or edges were lifting. No real evidence of pooling. It was solid. The only thing(s) left on the roof were 3 abandoned A/C units which were up on pallets.

Thanks for taking the time Jim.

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Looks like PVC.

EPDM is rubber, like a heavy rubber inner tube

There is one brand name of PVC called "Durolast". You can google them and from their website request an information package that includes a small sample of the product. Worthwhile for learning.

How do I know? I asked the same question a few years back. :-)

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I generally refer to that stuff as "TPO" (Thermoplastic polyolefin), but I believe it is interchangable with "PVC". I've sometimes found printing along the sheet edges on newer stuff.

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tn_200985164042_FirestoneTPO.jpg

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It does look like you have some (relatively minor?) ponding issues in that 2nd photo.

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TPO is not PVC.

Although TPO, PVC and CPE are all thermoplastic roof membranes, it's important to be able to identify each. For one example, there's been many issues with TPO formulations, resulting in failures not seen in PVC.

Anyone inspecting commercial or apartment buildings should really consider taking a course in commercial roofing. I certainly wasn't qualified to identify materials and their installation requirements before finding the proper training.

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TPO is not PVC.

Although TPO, PVC and CPE are all thermoplastic roof membranes, it's important to be able to identify each. For one example, there's been many issues with TPO formulations, resulting in failures not seen in PVC.

Anyone inspecting commercial or apartment buildings should really consider taking a course in commercial roofing. I certainly wasn't qualified to identify materials and their installation requirements before finding the proper training.

OK...my bad. I need to read up some more. I don't do commercial or whole complexes but I will get on condo roofs, when possible, for a quick gander at the common area roof. I may have mis-identified some stuff in the past, but I'm mainly looking for bad seams, ponding, etc.

So I have a question...What's in the photos that would make the first few responders believe it is PVC and not TPO?

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So I have a question...What's in the photos that would make the first few responders believe it is PVC and not TPO?

Good question Richard - and I don't have a good answer, except PVC is what I'm use to seeing and what 1st came to mind.

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TPO is more smooth surfaced than PVC; this is a fairly subjective analytical method, as the differences are very slight. You can see a little more scrim/fabric texture in PVC. Honestly, I've been fooled a couple times as the differences are minimal.

TPO was developed to blend the positive characteristics of EPDM and PVC. It has the UV and heat resistance of EPDM with the hot air weldable feature of PVC's.

And, it's white, so it's viewed as a more "green" roofing material.

I can't tell which it is from the photo.

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Yeah, trying to tell them apart by the scrim texture is pretty vague, or impossible. I had a rep try to show me and honestly, I'm not sure I could tell the difference even with him standing there pointing out the differences.

If it's newer, I'd guess TPO simply because that's the big push around here instead of PVC. If it's older, I'd guess PVC.

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OK, self correction because this is sort of a vague pathway......

Bill is right. The TPO has a slightly more visible scrim texture than PVC. I checked up, and I was wrong.

At least, I think I'm wrong. It's really hard to tell the difference between the two.

I do know that some of the early TPO's had a mega-problems with delamination/scrim separation, and none of the installers were welding it correctly. If it's older TPO, beware.

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Sorry guys, I don't get to many of these and want to be sure I am calling it the right product. Would this be EPDM?

My guess is TPO. I've seen a ton of PVC roofs and some TPO roofs. Every TPO roof I've seen has had plumbing vent boots that looked like the ones in your picture (the little stair-step jobbies). Some of them even had the letters TPO thoughtfully embossed on them.

Not one of the PVC roofs I've seen has had that style of boot on it.

- Jim Katen, Oregon

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So Jim, you would base an ID on the whether the roofer actually used the correct boots? Those are some pretty long odds.

Tom

Yes, perhaps. On the other hand PVC and TPO might be hard to distinguish from one another, but not when they're both sitting there on the same roof under your very own fingers. If they used the wrong boots, I'll bet that I could tell.

- Jim Katen, Oregon

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