Valley flashing is metal or membrane installed in roof valleys to prevent water intrusion and direct runoff safely off the roof.

Valley flashing is a critical roofing component installed along roof valleys where two sloped roof planes intersect. Its primary function is to protect the roof deck from water penetration by directing rainwater and snowmelt away from the joint and into the roof’s drainage system. Because valleys concentrate large volumes of runoff, flashing provides an added layer of defense beneath the roofing material.

Valley flashing is typically made from durable materials such as galvanized steel, aluminum, copper, zinc, or waterproof membrane systems. It may be installed as exposed flashing in open valleys or concealed beneath shingles or other roofing materials in closed valley designs. Material selection and installation method depend on roof type, climate conditions, and manufacturer requirements.

From a construction and code standpoint, proper valley flashing installation is essential for long-term roof performance. Codes and roofing manufacturers often specify minimum flashing widths, overlaps, and fastening methods. Poorly installed or deteriorated valley flashing is a leading cause of roof leaks, making careful detailing and routine inspection especially important in both residential and commercial projects.

Copper valley flashing can last 50 years or more, often outlasting the roof covering installed above it.

• Aluminum Flashing
• Base Flashing
• Cap Flashing