New roof, three closed valleys, no ice and water shield: should the owner make the crew redo them?

The owner laid out the problem on Reddit’s r/Roofing: the crew conceded that the membrane was left out of all three valleys but disputed that this breaks code. The owner’s hesitation is that tearing into the valleys would add nail holes to a brand-new roof.

The code side is clearer than the crew suggests. Section R905.2.8.2 of the 2022 California Residential Code, which matches the International Residential Code, says valley linings go down according to the manufacturer’s instructions before shingles are applied. For a closed valley it accepts a single layer of smooth roll roofing at least 36 inches wide, or a self-adhered membrane of polymer-modified bitumen that meets ASTM D1970. A valley with only the field underlayment has neither. The rule crews often cite, the ice barrier at eaves, is a separate section that applies only where ice has a history of backing up, which is not the issue here.

The shingle maker’s instructions add detail. For a closed-cut valley, GAF’s Timberline instructions call for GAF leak barrier laid at its full roll width and centered in the valley, nails kept at least 6 inches back from the centerline and field underlayment lapped at least 6 inches over the barrier. GAF’s limited warranty stays in force on a misinstalled roof but excludes damage caused by work that did not follow its printed instructions, so a leak traced to a missing valley membrane would fall outside coverage. Other brands publish their own valley details; check the instructions for the shingle actually on the roof.

The fix is to strip shingles on both sides of each valley, lay the membrane on the deck and reshingle. Membranes certified to ASTM D1970 must pass a test for sealing around nails, which covers the worry about holes beneath the valley. Get a written scope that uses new shingles in the valley courses, photos of the membrane before shingles go back on, and the product names. GAF requires warranty claims within 30 days of noticing a problem, and telling the contractor does not count as notifying GAF.