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Installing metal roof over built up roof

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Guest User
11/11/2006
I am replacing my built up roof with a metal roof. The pitch is 4/12. My roofing contractor said that the metal can be installed over the existing roof by stripping the roof with 1x4's or 1x5's. Two questions. Can the metal roof be installed over a bulit up roof this way? Do the 1x4's or 5's need to be treated?
Allan Reid
Dura-Loc Roofing Systems, Inc.
11/14/2006
The building codes have some restrictions but I believe you are allowed to go over provided that the gravel is removed and any blisters cut and tarred. As to the installation, generally you should not use the new pressure treated lumber as the copper in the preservative can react with aluminum in the metalic coating on the steel. Another consideration is that the building code calls for ventilation. If you have a vaulted ceiling, then you must provide a minimum of 1" of free vertical vented air which means strapping the roof vertically first. As to see the product approval on the roof you selected and it will dictate the limits on installation and how to comply with wind and fire codes if required.
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