This roof valley, over the years, had developed several leaks. We removed all old roofing material down to the wood deck, changed several sheets of plywood, installed a synthetic felt underlayment, and new shingles to match the existing shingles. When a roof valley leaks, the most effective way to stop the leak(s) is to start over. Applying roof cement of silicone usually makes the problem worse.
Billy Guyette - Montgomery native, roofing specialist