Fixing roof system from exterior
Climate zone 5 (SW Michigan), 12/12 pitch, cathedral ceiling with tongue and groove knotty pine interior. Believed roof system from inside out: T&G, Faced fiberglass, 2×12 rafters, plywood sheathing, ice and water on 100%, asphalt shingles. When sealing and insulating the flat top/attic areas last fall, damp sheathing and rusty roofing nails were visible. Not all cathedral areas are T&G, maybe 30% is gypsum board, roof is not simple, several valleys where venting is not possible. Ridge vent and marginally effective soffit vents where possible.
Roof needs to be replaced, don’t want to tear out all the T&G if avoidable.
Current options on the table:
1. Remove current roof (shingles and sheathing) to expose T&G, spray 4-5″ of 2# closed cell foam on the ceiling from the outside and replace sheathing, Ice and water 8′ up and around valleys, replace with new shingles.
2. Remove current shingles, remove Ice and water, fix any rotten sheathing, install membrane and standing seam metal roof.
The first option seems more correct to me since we will be sealing up the ceiling and creating a proper barrier, the second option is interesting since it is a seemingly small up charge for a steel roof, but I’m afraid we will rot out the sheathing again.
Please advise if you see alternatives, these are only the options that have been presented. Any suggestions are welcome. Let me know if more information is needed.
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