How often should you inspect roof flashing?
Updated July 2026
Give your roof flashing a real look once a year, and again after any major wind or hail storm. Flashing is the thin metal that seals the roof's weak points where shingles cannot: around chimneys, in the valleys, at plumbing vents and skylights, and along walls and dormers. It is also the single most common place roofs leak, well ahead of the shingles themselves. Most of the inspection happens from the ground with binoculars and from inside the attic; you rarely need to be on the roof to catch trouble.
What changes the interval
| Your situation | Interval | Why |
|---|---|---|
| Chimney flashing | Yearly + after storms | The counterflashing pulls out of the mortar joint over time and the sealant behind it dries and cracks |
| Valley flashing | Yearly | Valleys carry the most water on the whole roof, so rust or lifted metal leaks fast |
| Vent-pipe boots | Yearly | The rubber collar dry-rots and splits in 10–15 years, a cheap $20–50 part that causes a stubborn leak |
| Skylight flashing | Yearly + after hail | Skylights leak more than any other roof penetration; check the head and side flashing |
| Step flashing along walls and dormers | Every 1–2 years | Each shingle course has its own piece; one corroded or caulked-over tab starts a slow drip |
The cost of skipping it
What skipping it costs: resealing or replacing a section of flashing is a $300–1,500 job depending on where it is and whether a mason is involved at the chimney. Ignore it and the leak does its quiet work above the ceiling first: soaked insulation loses its R-value, framing and roof decking rot, and by the time a brown stain reaches the drywall you are into $2,000–10,000+ of interior, insulation, and structural repair, sometimes with mold on top. Flashing is pennies of metal guarding the most expensive water path in the house.
How to do it (20 minutes · DIY from the ground and attic)
- From the ground, scan every roof penetration with binoculars: chimney, vents, skylights, valleys, and wall lines.
- Look for lifted or bent metal, rust streaks, gaps where flashing meets brick, and any hardened or missing sealant beads.
- Check the vent-pipe boots specifically for cracked or curling rubber collars.
- Go into the attic on a bright day and look for daylight or water stains on the underside of the deck near those same spots.
- Reseal small gaps with a compatible roofing sealant; leave bent, rusted, or chimney counterflashing to a roofer.
- After any big storm, repeat the ground scan and check the attic the next time it rains.
Knowing the interval is the easy half. OnOtto reminds you at the right interval, and it won't let you snooze it into next year. Tasks persist until they're done, and completing flashing inspections schedules the next one automatically.
Put this on autopilot, free for 30 daysFrequently asked questions
What does failed roof flashing look like?
From the ground you will see metal that has lifted, bent, or rusted, dark streaks running down from a chimney or vent, and gaps where the flashing meets brick or siding. Up close, the sealant is cracked, chalky, or gone, and vent boots show splits in the rubber. Inside, the giveaway is a water stain on the attic deck or a ceiling ring directly below a penetration. Any of these means the seal has opened, even if the shingles around it look perfect.
Can I reseal flashing myself or do I need a roofer?
Re-caulking a small gap with the right roofing sealant is a fine DIY if you are comfortable on the roof and the metal itself is sound. Anything structural is a pro job: bent or rusted-through flashing, chimney counterflashing that is pulling out of the mortar (that needs to be re-let into the joint and tuck-pointed), and valley metal replacement. A roofer's flashing repair typically runs $300–1,500. Do not just smear more tar over old failing flashing; it buys a season and hides the rot.
How long does flashing last compared to the shingles?
Quality metal flashing (galvanized steel, aluminum, or copper) can last 25–40 years, often outliving one full shingle cycle. The weak links are the sealants, which dry out in 5–10 years, and rubber vent boots, which crack in 10–15. That is why flashing gets a yearly look even on a newer roof: the metal may be fine while the caulk that seals it has already failed. When you replace a roof, insist the flashing be replaced or reused only if truly sound.
Where do most roof leaks actually start?
Not in the field of shingles, where people assume, but at the transitions: flashing around chimneys and skylights, valley metal, vent boots, and wall step-flashing. Water always finds the seam. That is why a leak can show up on a ceiling several feet from the real entry point, having traveled along a rafter first. When you chase a stain, look uphill at the nearest penetration, then confirm from the attic. Related failures at the exterior caulk lines follow the same logic.