Metal roof over shingles with foam insulation

Guest User
We finished building our new log home 3 years ago. We have a cathedral ceiling in the great room. We have had a lot of ice dams that build up and have caused some internal leaking. We took care of the leaking but still think A LOT of heat is being lost through the roof. Putting more insulation is not an option without tearing the roof up. The ceiling inside is finished tongue&grouve. I want to know if it is possible to put a metal roof over shingles with an inch or so of foam insulation. Maybe with furing strips?
Guest User
Rod, It can be done. We usually use ISO board (better R-value than styrofoam). Typically, we use 2" or 3" ISO with 1/2 CDX or waferboard over that. There has been some jobs that we use lathes(furring strips). I would use 2x4's with 1&1/2 inch ISO board. The ISO comes in 4x8 sheets, cut it down the middle lengthwise. This gives you a 2 foot by 8 foot strip. Band the roof (all outside edges) with the 2x4. You then install a 2 foot wide strip of ISO butted against the 2x4 and then a 2x4 butted against your ISO. You do this all the way up the roof. Doing it this way ensures you a minimum loss on you ISO board. [email protected]
Guest User
Wade, Do you think a 1&1/2 inch will be enough to raise the R-value? Do I glue the ISO down or screw it? I want to DIY the project. So any advice is appreciated. Are the 2 foot wide strips so there is something to screw the metal roofing to? Do I have to worry about venting? I will have the help of a friend that is experienced in carpentry but a specialist is always better. Thanks
Guest User
Rod, Email me at [email protected] and I will give you my phone number and talk you through it. Wade
Todd Miller
Classic Products, Inc.
Thanks Wade.
Anna Lee
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Guest User
I'm doing metal roof on my double wide. Can I gule 1/2"form insulation to the shingle then screw it directly thru the foam, shingle and into the plywood. The foam does have a vapor barier. Any Idea?
An informed customer is our best customer.
From an installation standpoint, you are best suited to remove the shingles so that the insulation can lay flat on the deck. Insulation only works if it is in direct (no air spaces) contact with what it is trying to insulate. Given the textured surface of the asphalt and raised profile (if an architectural shingle) the foam will not be doing as good a job as it could be. I would screw the foam down, put a plywood top on it and apply your new roof.
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