Standing Seam On Sheathing

Guest User
I'm building a 50x100 hay/equipment shed and I am planning to install standing seam roofing over plywood sheathing with a layer of 30# felt between. Is this sufficient to prevent condensation without any other insulation and if not, what other insulation should I use and where should it go? The building won't be heated or otherwise conditioned. Also, when laying down the felt, how should it be applied? Should it run perpendicular to the panels with overlap like might be done under shingles and, if overlapped, how much? Or should it be run parallel to the panels and overlapped or not? My concern with the overlap is the step that will create for the metal to span. Maybe that doesn't matter, but not having done it before, I'd hate to find out I was making the wrong assumption! Thanks. Steve
Todd Miller
Isaiah Industries, Inc.
Because this building will not be heated and it also sounds like it will not be used for animal confinement and it also sounds like a building that will have a fair amount of air movement, I think you will be okay. Still I would not mind seeing a vapor barrier on the inside of the building. 30-pound felt should be okay even without a slip sheet on top of it since you are not in a horribly hot climate. You might though want t consider one of the new synthetic underlayments in place of the felt. Underlayment must be run horizontally and lapped per manufacturer instructions. I would suggest plastic cap nails for attaching it. The overlaps of the underlayment should not affect the roofing.
Eric Novotny
An informed customer is the Best Customer!
+1 to Todd's suggestions. You should not have a much lessened condensation potential given the lack of conditioning the space and what will probably be good air flow. A humidistat equip gable fan should help that much more. I prefer the synthetics (underlayment) over the felt and they are not that much more expensive in the end.

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