Metal roof underlayment .

[pat1016]

Building a 25x36 pole barn with a 12’ wall height. It was suggested to use double bubble under the metal roof which will be attached to purlins.
not crazy about this as I heard that this breaks down and flakes. Building will be unheated. And no plans to heat in the future. No insulation. Vented soffits, 2 foot overhang. Ridge vent and gable vents. Don’t want osb sheeting on roof.
location is NJ near the shore.
what is supposed to go under the roofing? Tyvek or similar? Put roofing felt on purloins where metal is fastened?
what about wrap on the siding?
Use insulation blankets?
thank you
Pat

 

[WisJim]

Every unheated uninsulated pole building I have seen has the metal fastened directly to the purlins.

 

[Copymutt]

No insulation, Use insulation blankets?
Sorry, lost me.
Any metal roof w/o a good underlayment will leak when the gaskets dry out. Underlayment is the primary reason roofs don't leak. Some sort of sheathing will be needed to attach the roofing felt or ice & water shield product. The catch here is the thickness & type of sheathing is determined by rafter spacing. I don't have wind rating or snow load requirements for NJ. But, I bet they are at least 30# sq. ft. Which also calls for sheathing.

 

[Adaylate]

I used a thin heavy duty fabric material under my metal roof on a shed. The material was almost like a heavy landscape fabric but wasn't. It kept condensation from forming on the underside of the metal.
Your metal roofing supply company should have it.
Good luck!

 

[Adaylate]

I should mention I had 1x4 skip sheathing on 2 foot centers on top of the rafters. That made it easy to lay the fabric.
No condensation and the birds didn't bother it!

 

[pat1016]

Thanks for the replies. A friend who has done over 9 roofs recommended 1/4” fan fold closed cell foam. They come in 4’x50’ sections. Has no problems here in NJ or at his buildings in Maine.
probably will put Tyvek on sides.

 

[PCustoms]

Thanks for the replies. A friend who has done over 9 roofs recommended 1/4” fan fold closed cell foam. They come in 4’x50’ sections. Has no problems here in NJ or at his buildings in Maine.
probably will put Tyvek on sides.

Seems like a waste of money to me.

I've never been in an insulated pole barn with roof sheathing and/or any form of underlayment under the tin.