One of the largest residential roofs we’ve completed (over 4000 square feet).  One layer removed and some minor plywood repair around the chimney.  Originally, the six valleys were all “exposed” – that is, the shingles were cut about four inches shy of the valley leaving the galvanized flashing exposed.  Although this is an acceptable, watertight application, it is usually considered unsightly and the galvanized steel has a tendency to rust.  We triple-coat all valleys (24″ aluminum flashing, inter-woven tar paper, and finally shingles).  We are also very proud of our method of making impeccably straight valley lines, very attractive from the ground.