Highest water volume on the roof.
Narrow flashing fails in the first storm.
Directs water in rather than wicking under.
Damming causes leaks in sound roofs.
Fewer joints along the run.
Fasteners and boots are more common causes.
Everywhere else on a roof, water travels down one plane and off the eave. In a valley, two planes converge and the combined volume runs through a single channel — often at high speed on a steep roof. Any deficiency in the flashing width, the panel cut, or the sealing gets found immediately and repeatedly. Most metal roof leaks that are not fastener-related are valley-related.
Valley flashing needs to be wide enough that water at peak flow cannot ride up under the panel edges — narrow flashing is a false economy that shows up in the first hard storm. Panels are cut at an angle to run alongside the valley, and that cut edge should be hemmed or turned so water is directed into the channel rather than wicking sideways under the panel. Those two details do most of the work.
Valleys collect leaves, pine needles and grit, particularly under trees. Debris dams water, water backs up under panel edges, and you get a leak in a roof that is otherwise perfect. This is the argument for clearing valleys as part of annual maintenance, and for being generous with flashing width on any roof that sits under a canopy.
First establish that it is the valley — water shows up well away from where it enters, and fasteners and pipe boots are more common culprits. If it is the valley, the usual causes are flashing that is too narrow, a panel cut that is too close, debris damming, or failed sealant at the top of the run. We supply valley flashing cut to length in your colour and can talk through the detail before you order.
Usually flashing that is too narrow for peak water volume, a panel cut too close to the channel, debris damming water, or failed sealant at the top of the run. Confirm it is the valley first — water surfaces well away from where it enters, and fasteners and pipe boots are more common sources.
Wide enough that water at peak flow cannot ride up under the panel edges. Wider is the safe direction, particularly on steep roofs, long runs, or anywhere under trees where debris will dam the channel. It is not a place to economise.
Sealant supports the detail; it should never be what makes it work. A valley relying on sealant to stay watertight will leak when the sealant ages. Correct flashing width and panel cut do the work, with sealant as backup at terminations.
Yes — cut to length in your panel colour, with no minimum order. Call (252) 375-3651 with your valley length and roof pitch and we will spec the width.
Tell us the size, your county and what you are storing. We quote from current steel pricing — no obligation, and we will tell you if a different size suits you better.
