Learn how to install roof valley flashing in this free roofing instruction video.
The valley flashing is laid between two valley battens and fastened through the top flange. Where the valley terminates at a fascia, the valley flashing should extend past the fascia a minimum of 3/4 of an inch. It must then be scribed to the fascia if required. Where the valley terminates onto a lower roof, the lower roof panel should be laid first. Valley flashing should be lapped a minimum of 4 inches and set in the beat of cocking. Ridged junctions and valley should be formed by standard sheet metal practice with notching and folding each piece in opposite directions, again set in the beat of cocking. It is important to apply granules with acrylic on any exposed cuts on the valleys to protect them from premature rust. Conditions of lower slopes and ice damming will require a lapse larger than 4 inches. Ice and water shields should also be considered in these cases.