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Old 04-16-2014, 10:11 PM   #1
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Metal roof underlay


I'm considering replacing a low slope (1.75:12) metal roof on the back of my house. I believe it is currently TPO but not positive. It is not leaking, and appears to be in good shape, but since this is an older house, insurance company is telling me that it needs to be replaced so that they have a correct date on it. The TPO(?) is currently covered with gravel and I was curious if I was able to remove all traces of gravel, if I could use the TPO as an underlayment for a metal roof, or if it has to come up. I think I would have to do strapping across it so that the thermal expansion of roof panels don't rub against, and other than that I see no problem with this thought process.
I've read nearly all the mixed opinions of Metal for lo-slope, and don't want to re-hash that if possible, since there seems to be no definitive answer. I'm on Vancouver Island so temperatures aren't extreme at any point.
Thanks for the help

Sorry, but yes this is a re-thread from another site, but there were lots of views but no help.

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Old 04-17-2014, 06:46 AM   #2
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Do you get snow? if yes then I would not recommend metal on that shallow a slope.

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Old 04-17-2014, 07:22 AM   #3
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If you get a ton of snow, single ply is probably better.

Double mechanical lock standing seam is pretty proven on low slope applications as well.
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Old 04-17-2014, 09:14 AM   #4
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good stuff, thanks for the help. Still haven't made a decision on it yet, still saving my pennies. Our snow is minimal at best, and yep was def looking to do the mechanical locking standing seam. That part I wont cheap out on.
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Old 04-17-2014, 01:19 PM   #5
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Rocks on a TPO? While not unheard of it would be loose laid rock other wise it would all end up on the ground.

I'm going to assume this is an BUR. The rock would need to be scraped down to smooth, then add your metal panels. you would also need a under layment then. TBH The best bet is to remove the existing roof in both cases.

A almost 2:12 is fine even with some snap lock panels, some manufactures will require sealant in the seam, others not. Double locks are great, but not exactly DYI friendly.
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Old 04-20-2014, 03:44 PM   #6
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Originally Posted by 1985gt View Post
Rocks on a TPO? While not unheard of it would be loose laid rock other wise it would all end up on the ground.

I'm going to assume this is an BUR. The rock would need to be scraped down to smooth, then add your metal panels. you would also need a under layment then. TBH The best bet is to remove the existing roof in both cases.

A almost 2:12 is fine even with some snap lock panels, some manufactures will require sealant in the seam, others not. Double locks are great, but not exactly DYI friendly.
I agree, I was thinking the same thing. This is a BUR and not a TPO. And the absolute best procedure on any re-roofing project is to remove the existing roof right down to the deck. On residential projects re-roofing projects I always replace the deck and go to the bare truss.

Regarding underlayment, on a low slope I would recommend a high quality ice and water shield. BlueSkin or CertainTeed WeatherGuard HT come to mind but there are many others. I always run sealant on seams no matter what the slope and locking standing seam isn't difficult at all. At least not for me, but then again I do it for 10+ hours a day sometimes.

By the way, I'm in Vancouver so I'm not too far away from you. PM me if you have any further questions.
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Old 04-21-2014, 12:26 PM   #7
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Regarding underlayment, on a low slope I would recommend a high quality ice and water shield. BlueSkin or CertainTeed WeatherGuard HT come to mind but there are many others. I always run sealant on seams no matter what the slope and locking standing seam isn't difficult at all. At least not for me, but then again I do it for 10+ hours a day sometimes.

By the way, I'm in Vancouver so I'm not too far away from you. PM me if you have any further questions.
Never said difficult, just not DIY friendly. As in not having the seam to finish the panels.
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Old 04-22-2014, 01:08 AM   #8
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Never said difficult, just not DIY friendly. As in not having the seam to finish the panels.
I agree. For those who aren't familiar with this it would be better left for a professional. Especially when you get to thicker gauges it becomes more of a challenge to work with.
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Old 04-22-2014, 10:02 AM   #9
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[QUOTE=grendel5269;1338101]It is not leaking, and appears to be in good shape, but since this is an older house, insurance company is telling me that it needs to be replaced so that they have a correct date on it.
******************************************
Change insurance companies. They're looking for things that need not be looked for.

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