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lagarto
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# Posted: 27 Feb 2012 01:47pm
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I live in NC Florida--if I use trusses, do I have to put down wood sheets (plywood) and tar paper under metal roofing? Why can't I make it like a typical pole barn (metal nailed on to 2x4s directly on trusses--will this be Ok if I insulated the ceiling below it? I guess as long as water doesn't get between the metal roof panels and drip down onto the insulation (sides will be enclosed)?
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MtnDon
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# Posted: 27 Feb 2012 05:45pm
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I've been inside some barns that were roofed with metal panels directly over the rafters (or rather, over purlins). With no sheathing it can and it does rain inside some of those barns. Rain from condensation on the underside of the roof. Condensation from the moisture in the air. It even happens here in the desert on the underside of the metal roof used to provide shade for animals. They've never complained.
IMO, the best roof to live under and keep dry under is always sheathed with OSB or plywood, then has a layer of #30 roofing felt or some type of synthetic weather resistant barrier. Then the final roofing; metal panels, shigles, whatever you like. That way there will be no condensation to trouble you.
There are areas (some parts of Oregon for one) where a metal roof on a house must be spray foamed on the underside if it does not have the metal applied over sheathing and a weather resistant barrier. Spray foam is a good way to insulate and not use sheathing if one is so inclined.
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Rob_O
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# Posted: 27 Feb 2012 05:49pm
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You will need panels rated for structural use, and the air space between the insulation and the roof panels needs to be ventilated like any other attic
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Rob_O
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# Posted: 27 Feb 2012 05:51pm
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And all that stuff Don said
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