Rebuilding the roof on a Deck house
We own a 1970s type post modern Deck House. As we found out the hard way in our first winter in the house, the roof doesn’t have any insulation. We have cathedral ceilings throughout the house (no attic) with tongue and groove 1 3/4″ deck boards on the ceiling, a layer of plywood, and shingles. Low pitched roof and we are in Zone 5 so less than ideal with an R-value around R-3. See attached.
We are looking at rebuilding the roof to accommodate rigid insulation over the roof deck boards. Both quotes we are entertaining are recommending: 6 inches of Hunter Poly Iso and 1/2 inch CDX Plywood than Shingles.
One quote is recommending an Grace Ice & Water Shield directly on top of the Roof deck boards, then rigid insulation, Plywood, and another Grace Ice & Water Shield for the full roof.
The other quote is recommendation, Ice and Shield only on top of the 6″ of Hunter Poly Iso and only for 9 feet to leading roof edge. The rest of the roof would have a Synthetic underlayment. Note that we have 2 feet of overhang on our roof.
The total R value of insulation would be R-34 plus the minimal R-value of the tongue and groove decking that we currently “enjoy.”
Our #1 goal is to ensure no more water penetration from ice dams. I’m curious what everyone thinks of this overall approach for a Deck House and which Grace Ice and Water Shield approach seems most appropriate.
Thanks for your insights!
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