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TOPIC: Underlayment

underlayment

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WHEN INSTALLING METAL ROOF OVER EXISTING SHINGLES, WHAT IS THE PROPER WAY? SOME COMPANYS SAY STRIP WITH 2 X 4'S FOR AIR GAPS. SOME INSTALL FELT PAPER, AND SOME GO ONTOP OF THE SHINGLES. THE MANUFACTUER ONLY RECOMMENDS A MOISTURE BARRIER WHICH COULD BE THE EXISTING SHINGLES. WILL FIBERGLASS SHINGLES HARM THE METAL ROOF IF APPLIED DIRECTLY ONTOP???
Guest User

10/31/2004
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The building code calls for a moisture barrier underlayment under the roof covering unless a product has been tested and approved without one. Each metal roofing system has differant installation criteria. Some are allowed directly over asphalt and some not and it varies between a vaulted roof assembly and an attic assembly. If you lay the metal over the existing roof, there is a good chance that the shingle stone and possibly the joints could telegragh through so if approved it is always best to lay a felt paper in between to help separate them much like a carpet underlayment. Best ask for their residential product approval report issued by the ICC and if they do not have one then that may be an indication and remeber vaulted roof assemblys require a minimum of 1" of vented air space under the roof covering.
Allan Reid
Dura-Loc Roofing Systems, Inc.

11/1/2004
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Or copy this URL: https://www.metalroofing.com/spirit/comment/4520/find/
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