An open valley is a roof valley where metal flashing remains visible between the cut edges of shingles. This type of valley is typically paired with valley metal, often a W-valley profile with a raised center rib.
Why It Matters
Valleys carry a large amount of water. An open valley can provide a clear drainage path when the valley receives heavy runoff, and W-valley metal can help manage water flow from the two roof planes. Open valleys are also common with rigid, thick, or less pliable roofing materials that cannot transition cleanly from one roof plane to another.
Common Problems
Common issues include crooked shingle cuts, exposed fasteners, undersized metal, poor underlayment, debris buildup, damaged W-valley metal, and mismatched valley design. Problems can also happen when a roofing material is forced into a closed-valley style even though the material is too rigid or thick to make that transition properly.
Building Codes & Industry Standards
Valley details should follow roofing material manufacturer instructions, underlayment requirements, and applicable code provisions for roof drainage and weather protection. Some products or profiles may require open metal valleys because of material thickness, rigidity, or installation limitations.
Exterior Echelon Notes
Exterior Echelon reviews valley design during replacement planning because valleys are among the most important water-management areas on a roof. When an open valley is selected, the valley metal profile, including whether W-valley metal is appropriate, matters.
