I’m about to build a post and beam barn. I’m going to have a wood stove in there at some point. With that said, I’m going to have a metal roof. Do I need to throw a wood subroof under the metal ? I was originally planning on doing horizontal strips on the rafters and just screw the metal roof to that.

You can have condensation issues with a metal roof.
The issues occur when there’s high humidity and enough radiational cooling occurs to make the moisture condense out of the air.
Won’t happen every day and If you have a ceiling you’ll never notice it.
I’ve not seen structural issues from it.
There’s some preformed metal with a anti condensation coating available, have not used it.
ABC Supply sells one product.
Should be less expensive than going from purlins to sheathing.
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Plywood would be best but I'm sure you could use strapping at 16" on center. I would go to the product page of the type of roofing material you're going to use for instructions on installations

Thanks Pete. Condensation is is what i was concerned about. I will look into that product. :)

I would contact supplier website to ask about condensation

I would contact supplier website to ask about condensation

I did. Condensation is an issue plus all the heat would just go through the metal. So a subroof it is. I just put up the first wall yesterday :)
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Eben, don't think you would need 3/4 exterior. Probably get away with something less expensive.
1/2" PT is around $40/sheet.

BTW, the PT now sucks. I just rebuild a 10 x 12 deck and had 5/4 PT decking that was half rotted and only 10 years old.

I know it is a barn, but at least price the Zip system 5/8 roof sheathing. brick colored, not the green 1/2". I have used it. Like it. Put some up last fall an covered it last week. Not visible change after out all winter.

I know it is a barn, but at least price the Zip system 5/8 roof sheathing. brick colored, not the green 1/2". I have used it. Like it. Put some up last fall an covered it last week. Not visible change after out all winter.

We use zip system frequently. It is fantastic. Roll the tape.
Not to beat a dead horse but the zip flashing tape is the most useful invention ever
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I decided that I am just going to lay down some 2” battens across the rafters and just screw the metal roof to those battens. The decision is because I don’t think I will put a wood stove in there.
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I decided that I am just going to lay down some 2” battens across the rafters and just screw the metal roof to those battens. The decision is because I don’t think I will put a wood stove in there.
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Yes… it’s a barn, noisy when it rains, the wrens can get in every spring at the eves, perfect place to rest and have a brew,,,,, life is good…. :-)