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Community and Q&A

Metal Roof Installation Over Asphalt Shingles

srivenkat | Posted in GBA Pro Help on

Hello Pros,

There was some hail damage to my 19-year-old asphalt-shingled roof last summer and I am considering a standing-seam metal roof, with the idea of thin-film solar panels affixed in between the seams sometime in the future. I am in the process of getting bids for the roof and have the below question:

Almost all the contractors are proposing roofing over the existing asphalt-shingles to avoid the extra cost involved with a tear-down of the shingles. Could this present problems in the present or the future? Could the asphalt rot before the metal roof is due for replacement decades from now?

Thanks in advance.

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  1. Expert Member


    I'm not wild about the practice, simply because I don't like kicking work down the road when it could be done now, but installing metal roofing over existing shingles works fine as long as they strap the roof first. You need the spacing to avoid the shingles abrading the backside of the metal panels, and to provide a flat substrate. Some roofers say a layer of paper in-between the two is enough, it isn't.

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