How to Flash the Hips and Valleys for a Metal Roof

Remove the old layer of shingles, if necessary, and prepare the roof deck for the metal roof installation. This involves clearing any remaining nails in the roof deck and removing the debris from the work area. This step is not necessary for new construction projects.

Cover the roof deck with roofing paper or tarpaper. Start at bottom edge of the roof with courses of roofing paper running parallel to the eaves. Add additional courses working up the roof with each course overlapping the lower course by about 4 inches. Staple the roofing paper in place with 1/2-inch staples.

Lay a course of roofing paper in the valleys and on the hips or ridges of the roof. These special courses of roofing paper cover the previous courses and run parallel to the ridge or valley.

Place the ridge flashing first. The rule for flashing is start at the top and work down and ensure flashing above goes over flashing below, to keep shedding water over the roofing material. Cut the ridge flashing to length using a tin snips or powered nibbler. Fasten in place using 7/8-inch galvanized screws. Cover the screw heads with clear silicone caulk.

Cut the valley flashing to size. The top of the flashing requires an angle cut to fit tightly against the ridge flashing or cap. If the valley is long enough to require multiple pieces of flashing, start at the bottom and place the top piece of flashing over the lower pieces. The valley flashing should create a 5-inch channel where water flows off the roof and to the ground. Fasten the valley flashing in place using 7/8-inch galvanized screws.