How long does flashing last?
Short answer. Roof flashing metal itself often lasts 20 years or more, with galvanized steel and aluminum commonly matching a shingle roof's life and copper lasting many decades. In practice flashing usually fails sooner because of how it was installed, dried-out sealant, rust at cut edges, or mortar joints letting chimney counterflashing loose, so it should be inspected regularly and usually replaced with the roof.
By material
- Galvanized steel: common and strong. The zinc coating protects it for many years, but scratches and cut edges rust first.
- Aluminum: does not rust and bends easily; it can corrode where it touches wet masonry or incompatible metals.
- Copper: the longest lasting, often 50 years or more, and used on high-end homes.
- Lead: soft and long lived, used for some chimney work and pipe boots.
Why flashing fails before the metal wears out
- Sealant dependence. Flashing that relies on caulk instead of laps fails when the caulk dries out, often within a few years.
- Counterflashing in mortar. Chimney counterflashing set into mortar joints loosens as the mortar weathers.
- Face nailing. Nails through exposed flashing leak and rust.
- Missing pieces. No kick-out flashing at the bottom of a wall, or one long strip used where individual step flashing belongs.
- Storm damage. Wind lifts edges and hail dents soft metal.
Replace or reuse during a reroof?
Step flashing along walls and chimneys is woven into the old shingles, and tearing off the roof usually bends or damages it, so most quality reroofs replace it. Counterflashing set into brick can sometimes be reused if it is in good shape, but rusted or loose pieces should go. Reusing worn flashing under a new roof is a common shortcut behind early leaks. See roof flashing explained and chimney leaks and crickets.