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A roof valley, the internal angle formed where two roof planes meet and slope toward each other, concentrates more water flow per square foot than almost any other part of a roof, which is why the method used to construct it matters so much to long-term performance. Three approaches have dominated residential roofing for decades, and each handles the same basic problem, directing converging water down and off the roof, in a different way.
An open metal valley uses a continuous strip of formed metal, commonly galvanized steel, aluminum, or copper, running the length of the valley with the shingles from both adjoining roof planes cut back and trimmed along chalk lines a set distance from the centerline, typically around two inches on each side, leaving the metal visible down the middle. This method sheds water efficiently because it relies on a smooth metal surface rather than overlapping shingle edges, and it is often specified in colder climates because it handles ice and heavy runoff well.
A closed cut valley, sometimes called a cut valley, has shingles from one roof plane running uninterrupted through the valley while shingles from the adjoining plane are cut along a line roughly two inches back from the valley centerline and laid over the top. An underlayment or ice barrier is typically installed beneath the shingles in the valley regardless of which method is used above it. A woven valley interlaces shingles from both planes across the valley in alternating courses with no cutting at all, a method that has become less common as manufacturers have moved toward laminated architectural shingles that do not weave as flexibly as older three tab products.
Each method carries its own maintenance profile. Open metal valleys expose bare metal to sun and weathering over the life of the roof, and while modern factory finishes resist corrosion well, older or lower gauge metal can eventually pit or discolor. Closed cut valleys hide the metal or ice barrier beneath shingles but concentrate wear along the cut shingle edge, where granule loss can appear first. Woven valleys distribute wear across more overlapping material but create a noticeably thicker, bulkier profile at the valley centerline that some installers and homeowners consider less clean in appearance than an open metal valley.
The construction type present at a given roof affects several practical claim-related questions, including how the valley is repaired if only isolated shingles are damaged, whether matching materials remain available, and how a valley should be reconstructed if the roof is fully replaced. Manufacturer installation instructions generally specify which valley methods are approved for a given shingle product, and mixing an outdated woven approach with a modern laminated shingle can create both an installation problem and a warranty question. Inspecting a valley in the field involves examining the shingle cut lines or metal for granule loss, hail impact, or wear patterns distinct from the surrounding roof field, since valleys often show damage differently than open roof planes due to their steeper effective water flow and different sun exposure. The choice of method for a valley being reconstructed is generally a matter between the property owner and the contractor performing the work, guided by current manufacturer specifications and code.
This article is general education about how the appraisal process commonly works. It is not legal advice, and specific procedures can vary by state and policy.
Russ Lis is a working property insurance appraiser and umpire based in Minnesota, serving clients nationwide. Contact Appraisal Resolution.