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Discussion Starter · #1 ·
I Currently have a metal roof over a 12x16 deck which leaks in the lower corner where the upper valley empties onto it. I know I messed up and the metal roof was never designed for such a low slope. we might get 1" of snow and it typically melts in a few hrs so snow load is not a concern.

I will be extending the roof line another 20 feet and plan to replace the entire roof. I was thinking of using TPO and gluing it to the osb sheathing. to prevent leaks I would have the TPO membrane go a couple of feet up the exsisting shingled part of the roof. Location is Charlotte, NC and roof faces the North back yard which no one sees so no one will ever see it.
raising the roof pitch would be pretty expensive and even if I could the max pitch I could get is about 12:3.

thanks for any advice.
 

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Tpo is a good choice, as would be EPDM. However white epdm is pricey, while the standard color for tpo is already white. I would use a recovery board as well, to isilolate the mebrane from any framing/sheathing movement and to give a smoother appearance to final product.
 

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Discussion Starter · #3 ·
Tpo is a good choice, as would be EPDM. However white epdm is pricey, while the standard color for tpo is already white. I would use a recovery board as well, to isilolate the mebrane from any framing/sheathing movement and to give a smoother appearance to final product.
thank you, I googled recovery board, it's just fanfold insulation??? i assume that keeps the surface of tpo a little bit cooler so it warps less?
 

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thank you, I googled recovery board, it's just fanfold insulation??? i assume that keeps the surface of tpo a little bit cooler so it warps less?
It's similar, but 1/2in (or greater) thick and designed to be compatible with the glue. Comes in 4x8ft sheets. There are two kinds, one made with isocyanurate foam and the other made of a material similar to homosote.
 

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thanks, what is best way to put tpo under the exsisting shingles? I assume I just pry bar up the shingles and slip the tpo under it and use some mechanical fasteners at an angle to hold it?
Best is to remove 4-5 courses, let the tpo go up the slope as far as possible (12in minimum) tack the top edge down and replace the shingles, leaving the bottom course off.
 
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