Installation & Venting over Foam

Guest User
4/17/2017
I'm building a small "tiny cabin" and in the process of ordering a roof. Leaning towards metal. The structure is in the mountains of North Carolina. We have tons of rain in the summer, so I want to make sure I do this right. The temperatures are extreme, summers it can be 90-100* and winters can be down to 0* for a week or so. We won't be living in this, but more of a weekend getaway. It's a small roof, only about 16' x 20' and 3 1/2:12 pitch. Cold roof. I've got ZipWall decking down. My hope was to use 2" XPS foam board over the decking and then a layer of underlayment over the foam. I would like to create some sort of airflow between the foam and metal roof. I have looked at the Corvent systems for both the eave and decking. Would there be another option to create airflow on the decking? I know I could use 1x4" lathe but I would have to run them horizontal, which would block the vertical air flow to the top of the roof. I don't think I'll need an underlayment under the foam, since the ZipWall system acts as one already. Would it hurt to have one on top? Should I use an Ice & Water Sheild? Any help would be greatly appreciated!
Todd Miller
Classic Products, Inc.
4/17/2017
I think that underlayment on top of the foam is wise. I would probably just use a synthetic rather than ice and watershield. I would suggest vertical purlins and then horizontal purlins followed by the roofing, allowing for ventilation. You could use the Cor-A-Vent products for your air intake and exhaust. Make sure that the metal roof you choose is approve day its manufacturer for installation over battens.
Guest User
4/24/2017
Thank you for the reply Todd. I didn't realize some metal roofs were not designed to install over battens. Looks like the standing seam that is made in Asheville, we are looking at, is best to have over a solid deck. Do you know of any standing seam roof manufactures that it is OK to install over battens? Trying to avoid the cost of another deck above air gap.
Todd Miller
Classic Products, Inc.
4/24/2017
I believe that Fabral, McElroy Metals. ATAS, and Metal Sales would all have "structural" standing seam options available to you.
Guest User
4/24/2017
Great, thank you for your help Todd. Metal Sales I can find at 84 Lumber and they have a manufacturing place in NC. I'm assuming with "structural" panels these can be installed over battens? Thanks again
Todd Miller
Classic Products, Inc.
4/24/2017
That is correct. Good luck!

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