Joseph Peterson
1/24/2018
Hi I’m new to the form, thank you for taking the time to read my question. I’m about to start building a small cabin 16 x 20 with a shed roof. I’m building it out of Hemlock that we cut down from the property. I want the hemlock rafters (2x10)and hemlock roof sheathing (1x8) to be visible when viewed from below. My concern is getting some R-value on the roof. What is the best way to get some r factor in this scenario? Can rigid foam be applied on top of the Hemlock roof sheathing and then metal roofing put on top of the foam? Thanks Joe
Info @windowsonwashington.net
An informed customer is our best customer.
1/24/2018
Yes. How tight are the gaps going to be on the 1x8? Rigid foam with a customer rake edge and drip edge is your best approach here.
Joseph Peterson
1/25/2018
Eric, Thanks for the reply. The 1x8s will be butted tight so you can’t see the foam when looking up. Would this design need additional battens ontop of the foam to prevent fasteners from deforming the metal if overtighented?
Info @windowsonwashington.net
An informed customer is our best customer.
1/25/2018
Okay. In that case, I would seal the topside of the decking some some peal and stick Ice/water for an air barrier prior to the installation of the foam. This would make sure that there was no mixing of the outside air with inside air and would help with the condensation concerns. After that, proper thickness of foam attached to the structure prior to the roof and/or sleepers.

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