Metal roof panels over OSB... condensation?


  #1  
Old 07-21-08, 04:05 PM
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Metal roof panels over OSB... condensation?

What is the preferred method to install metal roofing in an
arid climate (Texas) over a 2x4 framing/OSB deck. The
manufacturer says the metal panels can be installed over OSB
or on 1x4 purlins or even 2x4 vertical runs and then 1x4 or 2x4
purlins.

The area under the roof will be heated and insulated with
fiberglass bats and I want to avoid condensation problems.

Should I screw the panels directly to the OSB(with felt) or
would 1x4 purlins be a better choice? Or should I go with 2x4
verts with purlins to allow airflow all the way to the ridge?

Anyone use rigid foam under metal panels?
 
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Old 07-21-08, 10:48 PM
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Location: rockland county,new york
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if you have enough insulation to keep heat from escaping,then condensation isn`t a big problem,I would use tamko high temp underlayment for metal roofs on plywood,then use red rosin paper as a slip sheet as the panels need to expand and contract,or you will get oilcanning---the vertical 2x4s with the firring strips would also work btw,and provide better ventilation,but if you`re attaching to a heated wall,you don`t want that
 

Last edited by the roofing god; 07-21-08 at 10:50 PM. Reason: add details
 

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