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TOPIC: DIY - Do It Yourself

Rigid insulation over old roof

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Hi: I have a remote cabin in Ontario. It is heated 6 to 7 times each winter for 2-3 days. Pitch varies from 3:12 to 12:12. Shortest length of panel is 16'. The existing roof is mineral face roll roofing over 30# felt over 2" rough sawn decking on log timbers. I plan to place 2'x8'x2" rigid foam between 2" x2" stringers nailed parallel to the ridge line with metal panels perpendicular on top of that. I plan to face the eaves and gable ends with 2" x 4" strips. This leaves a flat surface bounded by 2" lumber with 24" OC stringers for fastening. My questions: 1. Sound OK? 2. OK to leave the existing roll roofing in place? 3. Could I go to 48" OC stringers and increased space between fasteners? Thanks for any help you can offer
keith summers

6/30/2008
Your original plan sounds good. Is there any ventilation there at all now? Todd Miller
Todd Miller
Isaiah Industries, Inc.

7/13/2008
There is no insulation at all on the roof at this time. The plan is to have this sequence from the interior out: 2" rough sawn planking, existing 30# felt, existing mineral face roll roofing, 2" pink foam, metal roof panels.
Guest User

7/15/2008
Keith, I would install an underlayment over the rigid insulation. We use stress plates to fasten the insulation and underlayment.
Guest User

7/15/2008
Do you want the 3:12 sections to be "walkable?" Does it make any sense at all to run the 2x2s perpendicular to the ridge to facilitate ventilation? I just insulated a 2:12 roof with 3 1/2" rigid foam w/2x4s on edge @ 16o.c.. However, if you are only heating it a handful of times... your plan with 2" foam should yield R13?
Guest User

7/17/2008