Roof flashing is metal (or sometimes rubberized material) installed at joints and edges so water is steered away from places roofing can’t cover. When it rusts, lifts, cracks or loses its sealant, water gets behind it, and the leak often shows up nowhere near the damaged spot.
Where flashing lives, and where it fails
| Location | What the flashing does | Common failure |
|---|---|---|
| Where the roof meets a wall | Step flashing is layered with each course of shingles to shed water away from the wall | Bent, rusted or missing pieces; siding or stucco pushed against it with no gap |
| Valleys | Channels water where two roof planes meet | Corrosion, debris backing water up, nails driven through the metal |
| Around chimneys | Base flashing plus counterflashing tucked into the masonry | Sealant cracking, counterflashing pulling out of mortar (see chimney leak repair) |
| Skylight perimeters | Directs water around the curb | Seams opening up, sealant failure; see skylight leak repair |
| Eaves and rakes (drip edge) | Keeps water from running behind the fascia | Gaps, missing sections or being installed under rather than over the underlayment |
| Penetrations | Boots and collars around pipes and vents | Rubber cracks with sun exposure; see roof vent leak repair |
Signs that point to a flashing problem
- Stains on a ceiling or wall near where the roof meets a wall, a fireplace or a skylight
- Leaks that only happen with wind-driven rain from a particular direction
- Visible rust, lifted edges or gaps in the metal at roof junctions
- Dried, cracked or peeling caulk or roofing cement, which often means someone patched it before
- A roof that otherwise looks sound but still has a recurring leak
Why caulk alone usually isn’t the answer
A tube of sealant is the standard first response, and it often works for a season. But sealant weathers, shrinks and cracks, and flashing that has failed structurally needs to be re-set, replaced or properly integrated with the surrounding roofing. Roofers who see repeated sealant patches on the same junction will often recommend replacing the flashing outright, because the patching only delays the repair.
What a repair involves
- Exposing the problem areaSurrounding shingles are lifted or removed so the flashing and the roof deck beneath can be inspected.
- Assessing the deckIf water has been getting in for a while, the wood underneath may be soft or stained and need replacement.
- Installing new flashingPieces are layered so each one sheds water over the one below, then integrated with underlayment and shingles.
- Sealing only where appropriateSealant is a secondary line of defense at the edges, not a substitute for correct layering.
Flashing and the rest of the roof
Roof-edge flashing, the drip edge, works together with gutters, and the Creekside page explains how drainage problems and edge leaks feed each other.
Flashing problems are among the most common reasons a house leaks, which is why a competent roofer looks at it first. If you’re seeing a stain but not sure where the water enters, the broader overview of local roof leak repair explains how contractors trace leaks. For leaks after wind or heavy rain, storm damage roof repair is the related page to read next.
Roof flashing questions
Can flashing be repaired without replacing the roof?
Usually yes. Flashing work is localized, with surrounding shingles lifted and reinstalled. If the roof is near the end of its life, a roofer may suggest addressing both at once.
How long does flashing last?
It depends on the material, exposure and installation quality. Metal flashing can last a long time, but sealants and rubber components tend to wear out sooner.
Is flashing leak repair an emergency?
If water is coming in during rain, treat it as urgent. A small, intermittent leak can often wait for a daytime appointment, but don’t let it go through the whole wet season.
Can I seal the flashing myself?
A temporary dab of sealant on a ground-accessible spot may buy time, but getting on the roof is risky and incorrect sealing can trap water. Leave roof access to professionals.
Related services
Leak near a wall, valley or chimney?
Call to be connected with an independent roofer who can trace it and repair the flashing.