The lifespan of roof flashing depends heavily on the material used, installation quality, and environmental conditions, but generally quality flashing should last as long as the roof covering when properly installed. Galvanized steel flashing, the most common economical option, typically lasts 15 to 25 years before rust develops, with shorter life in coastal, humid, or industrial environments where corrosion is accelerated. Aluminum flashing lasts 20 to 30 years and resists rust but can corrode when in contact with dissimilar metals or concrete. Copper flashing is the most durable, lasting 50 to 100 years and often outlasting two or three asphalt shingle roofs, developing a protective patina. Lead flashing also lasts 50 plus years. Stainless steel flashing lasts 30 to 50 years. However, lifespan is greatly influenced by installation quality. Flashing installed with proper step flashing techniques, integrated with shingles in overlapping layers and sealed with compatible polyurethane sealants, lasts much longer than flashing that relies solely on caulk. Environmental factors like salt air, acid rain, heavy snow, ice dams, and thermal movement can shorten lifespan. Flashing should be inspected every 2 to 3 years for rust, cracks, gaps, or separation. When replacing a shingle roof, which is typically every 20 to 30 years, flashing should always be replaced as well, as reusing old flashing is a common source of leaks.
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