Metal on 2" iso screwed to osb

Tooger Smith
This is a good site. Second question. I found a similar question from 2 or so years ago. Just wanted to check again. New construction. Vaulted ceiling. 2 x 12 rafters on 16" centers. 7/16 osb for decking. If I put two layers of iso board (one inch each) directly on the sheathing, can I then put the metal sheets directly on the iso boards and screw them to the sheathing? I am thinking then to cut and tightly and fit 1-2" iso inside directly against the sheathing, then put rock wool to "fill" the cavity. Then car siding and/or drywall. Thank you for your time. I feel like I have been to college again after spending so many hours researching this vaulted ceiling thing. But there is no question about metal for roof and siding. Chief and I live in a three deck pole barn originally built for a week end getaway. Open cell sprayed directly to the metal walls with wood planks for the inside. The roof has vaulted ceilings with purlins, bubble wrap and 4" open cell. But I am afraid to try only that with this house. It is of course my daughter-in-love's fault. That is what she wants.... can I say "No". Not a chance! :) Tooger
Eric Novotny
An informed customer is the Best Customer!
Foam to the inside is probably overkill to be honest. I would prefer to have the metal directly affixed to plywood as compared to going through 2" of foam ideally. Have you ever looked at an above roof vented deck design? Save the foam to the inside and spend a bit more for another layer of sheathing and some 2x4s. You can get the best of both worlds then.
Tooger Smith
Thanks, Eric. How about this. I can get iso board at a really good price. So and since our rafters are 2 x 12 @ 16 in oc, notched and strapped to the 2 x 6 wall and notched and strapped on the LVL beam (they are resting on the top of the lvl), nail the purlin vertically (as we usually do on a pole barn) then jam 22.5 in of ISO board three inches thick, then jam the next purlin, .iso board, etc up the roof. Screw the metal directly to the purlins. Inside, spray an inch of closed cell, then "fill" the cavity with rock wool batts or open cell, then drywall and/or car siding. That would give an air space and the ridge could be vented and interior sealed with the spray foam. Purlins make for good support of the over hang. Perhaps membranes could be used also or in place of the inch of closed cell since closed cell is so expensive. What do you think? As always, I appreciate your feedback. And anyone else's also. Thanks
Guest User
Questions: - What's the pitch on the roof - What kind of ISO are you getting - Are you going to need to walk this roof

If you would like to reply to this thread, please log in. If you do not have an Ask the Experts forum user account, create one here.

Find a Professional

Get Started Today

Take the first step to increasing the value of your home with a great looking, durable, fire resistant and energy efficient metal roof. Browse our list of qualified MRA Member Roofing Professionals in your area for a free consultation and estimate.