How long should skylight flashing last?
Short answer. Properly installed metal skylight flashing should last as long as the shingles around it, roughly the life of the roof, because aluminum and coated steel flashing do not wear out quickly. When skylight flashing fails early, the cause is almost always the installation, sealant used in place of real flashing, or debris and rust, and the flashing kit should be replaced whenever the roof is.
What actually wears out
- Sealant, not metal. Installs that rely on a bead of sealant at the head or corners lose that seal within a few Georgia summers. A properly lapped kit does not depend on it.
- Gaskets on the unit. The rubber gaskets and glazing seals on the skylight frame dry out on their own schedule, often well before the metal flashing.
- Painted or galvanized steel on older or site-built flashing can rust, especially at the head, where debris holds water.
- Exposed nail heads left by a sloppy install.
Why flashing is replaced with the roof
Step flashing along a skylight is woven between shingle courses, so tearing off the shingles means pulling or bending it, and reused pieces carry old nail holes and kinks. Skylight makers sell flashing kits matched to each unit size and style, and a new kit at reroof time costs little compared with a leak into a finished ceiling. If the skylight itself is near 20 years old or its glass is fogged, replacing the whole unit at the same time is usually the better value.
Signs the flashing has failed
- Water streaks down the drywall shaft from the top corners, especially in wind-driven rain.
- Stains on the ceiling just downhill of the skylight.
- Visible rust, lifted metal or heavy tar patches at the head.
- Pine needles packed against the uphill side, holding water.
Drips that come from the glass edge, or that appear on cold, dry mornings, are more likely failed seals or condensation than flashing. See replacing skylights with the roof and roof flashing explained.