Thread: Standing Seam Metal roof covering

Do manufacturers allow the standing seam metal panel roof covering to be installed on top of asphalt composition shingles?

brian

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You would have to check with the manufacturer, but this is a common installation. The old shingles will help protect the decking from condensation. I'd have to look it up, but I'm pretty sure that at least in OR, you can install a metal roof over 3 layers of comp, because it does not add much more weight to the roof.

Last time I looked the answer was 'No.'

At least not without first installing some type of paper or recovery board over the shingles to prevent the granules in the shingles from scratching into and through the finish on the back of the metal roofing panels and to also serve as a slip sheet to allow the metal roofing to expand and contract over the shingles. And I am not even sure this is approved by the metal roofing manufacturers - I do not believe it is in their installation instructions.

I didn't think this was proper installation , and beside, the must of run out of panles because the panels end about 18 " from the rake end exposing the comp shingles and allowing water to run under the panels.

And never mind the screw fasteners installed on top of the seams...the list went on....

Always start with a clean deck and the recommended underlayment

Would you recommend removing both roof covering and starting over?

Originally Posted by brianmiller

Would you recommend removing both roof covering and starting over?

BM: Yes.

Originally Posted by A.D. Miller

BM: Yes.

Ditto. No more short cuts for those apes.

Have seen metal roofs fastened to spaced strapping placed over asphalt but never metal directly on asphalt, the idea is to have an air space under the metal to dissipate heat and reduce expansion.

Brian,

I'd be careful with my report on this one if I were you. After spending a few minutes Googling your question, the answer seems to be that it's just fine to install a metal roof over shingles. You may need to install felt, wood strips, etc. depending on the manufacturer. You could end losing credibility if you start making an issue of something that may in fact be a non- issue.

Here's one small write up on the subject: Put a New Cool Metal Roof over Your Old Asphalt Roof - Metal Roofing Alliance eNewsletter Archive

Adding a metal roof over existing shingles doesn't seem like an issue to me at all. Wouldn't installing metal over an existing asphalt roof instead of doing a tear off first be considered a green building technique?

the must of run out of panles because the panels end about 18 " from the rake end exposing the comp shingles and allowing water to run under the panels.

And never mind the screw fasteners installed on top of the seams...the list went on....

Well,

that sounds like a crap installation.

It sounds like you have a typical shop style roof with exposed screws holding the panels down. Now, that is a problem, because they are know for leaking. Those should not be used over a residential structure....

This is seemingly an old thread, but I'll add my two cents... You should better discuss this question with a manufacturer, but oin any case this is a common installation. Such shingles can protect the decking from condensation that is really important. But I may be wrong.

Review 705.3.1 of the ICC Existing Building Code (unless your area has not adopted the Existing Building Code, or has adopted a different Existing Building Code, in which case review it).

Recovering a roof as certain specific requirements.