I am having my roof replaced next week. Per Owens Corning’s (Duration shingles) installation instructions, I can either 1. cover the entire roof in ice and water and install shingles directly over that or 2. do valleys and eaves with ice and water and then a double layer of synthetic underlayment that’s half lapped over every sheet.
All peaks of my house have ridge vents and soffit intakes. I will own the house long term so I’m trying to think forward to the next time the roof needs replacement and they have to replace all decking because of the existing ice and water. Currently have a leak and because of that I’m leaning full ice and water coverage. I live in New England. My roofer said he’ll do whatever method I prefer since that’s what OC says. Thank you in advance.