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I agree, no less than 4/12 but the sheathing must be layered 100% with Ice & Water memebrane first.
Recommended not less than 4:12 pitch. Also would advise in Western NC to install ice & water guard in place of standard underlayment.
The minimum pitch for an asphalt roof for Asphalt shingles is 2/12 or more as long as you use at least one layer of ice and water shield and one layer of synthethic felt under the architectural shingles. I would never use a three tab shingle on this low pitch roof. Below 2/12 pitch, I would use either an EDPM Membrane or the Resisto 2 0r 3 ply roll roofing membrane system.