Unvented slate roof: Best underlayment to prevent sheathing rot?
We are removing and resetting our slate roof in southern Oklahoma. So, a somewhat hot and humid climate without too much cold weather. The attic space is unvented and a conditioned space with about 6″ of open-cell spray foam. So, I guess you would call it a “hot roof” of the slate variety. The roof sheathing is made of 1 x 12 boards with no gap really. My question is what is the best underlayment for this situation? The contractor would like to use the peel & stick ice/water shield, but is also fine with the 30# felt paper. It is really just a matter of cost to us. The ice/water shield would give me a little more comfort about any future leaks, but would there be a risk of the sheathing rotting? Or, would the rot risk be more with the felt paper? (Please note, that rigid foam on the exterior is not an option.)
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