Valley Metal Liner

Valley metal is a piece of rolled metal flashing fabricated to protect roof valleys from leakage, and from being damaged in the event someone or something causes enough pressure to otherwise damage the roof underlayment and roof covering. Copper or galvanized steel work best for open valley metal. Aluminum may also be used but its better to use to heavy-gauge color-coated aluminum. The mill-finish aluminum that is commonly sold won’t last nearly as long. The valley metal used for an open valley should be at least 24 inches wide allower for 12 inches in each side of the valley. Each piece of valley metal should be no longer that 8 feet long due to thermal expansion and contraction, and should overlap each other by 6 – 8 inches. The valley metal should be fastened in a way that allows for thermal expansion and contraction. If you just nail it in along the edges the thermal movement will destroy the metal over time. Instead you can butt the nail shank to the edge of the metal and nail it down so the nail head slightly touches the valley metal without denting it. The nails must be made of the same metal as the valley liner to avoid a reaction that may cause galvanic corrosion. Another way to fasten the valley metal in place is by fabricating clips that will engage with a hem along the edge. In the recent years many roofers have chosen to forego valley metal using ice-and-water (peel-and-stick) instead. There are many debates and pros-and-cons of valley metal vs peel-and-stick that can be found all over the web.