sheathing or perlins?

guest guest
I am not familiar with metal roofing in a residential application. I have seen pole barn/storage buildings use perlins as opposed to full sheathing. Is this acceptable for a residential application? I am well versed in insulation and ventilation issues for attic spaces and have the ability to ensure great ventilation for moisture issues that may occur.
David Stermer
Guest, Thanks for your question. It depends on the type of the metal roof panel that you select. It is common for residential panels to be designed for applications over sheathing and not have the capability to span between purlin supports. If you use a panel able to span between purlins, such as those commonly used in pole barn construction, you certainly should be able to avoid the sheathing and just use purlins. Be aware that in typical residential construction the sheathing also provides stability for roof trusses and that leaving the sheathing out may effect the design of the trusses. Regards, David Stermer
Eric Novotny
An informed customer is the Best Customer!
What type of metal roofing were you considering? Each application has its own set of decking and support requirements as David stated. Be aware that regardless of the ventilation approach, you will be very likely have condensation form on the underside of the panel in an exposed application. Unless you have a completely sealed attic floor, there is enough moisture carried on bulk air loss that you will have some condensation issues in about 95% of the cases.
Guest User
To avoid condensation concerns, plan on insulating between the rafters with closed cell spray foam.
Eric Novotny
An informed customer is the Best Customer!
Jason, Using cc SPF is not the only cure for condensation control but it is certainly one of the better and more easy to install and not get wrong applications.
Todd Miller
Isaiah Industries, Inc.
I am a little surprised you have never had condensation issues. I'd have some concern that other things down the road to make the home tighter (such as new windows or something) could be a tipping point to cause attic condensation. If you added decking, or went the radiant barrier way, you could create a capsulated airspace or even a vented airspace beneath the metal roof panels and that will help with summer efficiency.

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