Every autumn, we meet the same homeowner. Their chimney has been "fixed" twice — once with a tube of roofing cement, once with a fresh bead of sealant — and every winter the stain on the ceiling comes back a little bigger.
The problem usually isn't the patching. It's that the flashing itself was finished, and nobody said so. Sealant can rescue sound metal. It cannot rescue metal that has rusted through, pulled away, or been installed wrong from the start.
Here are the seven signs we look for on Covina roofs when we decide whether flashing can be repaired or needs to come off and be replaced — and how you can spot most of them yourself, from the ground.
First, a 30-Second Chimney Flashing Refresher
Flashing is the metal system that seals the joint where your chimney passes through the roof. It has three main parts: step flashing woven into the shingles along the sides, counter flashing cut into the mortar joints of the chimney itself, and the apron and head pieces on the downhill and uphill faces. When all three work together, water sheds around the chimney like it isn't there. When any one fails, water gets behind the system — and that's when the signs below start to appear.
The 7 Signs
1. Rust that has eaten through — not just colored — the metal
Surface rust on galvanized flashing looks alarming but can sometimes be cleaned, treated, and sealed. Rust-through is different: pinholes, flaking, sections that crumble at the edges. Run your eye along the flashing after a dry week. Orange streaks below the flashing on the shingles or brick mean water is already carrying corrosion products out of the joint. Once metal has perforated, no coating restores it. That section — or the whole system — needs replacement.
2. A ceiling stain that keeps growing back
A water stain near the fireplace that reappears every rainy season, especially one that's been "fixed" before, is the classic signature of flashing that has failed structurally. Stains mean water is traveling — often along rafters — and the interior damage (wet insulation, softening drywall, eventually mold) costs more than the flashing ever would have. If you're on your second stain, stop paying for patches.
3. Flashing visibly lifted, bent, or separated from the chimney
Flashing seals by contact. Metal that has pulled out of the mortar joint, curled at the corners, or lifted off the roof deck leaves a visible gap — and wind-driven rain, which Covina gets plenty of during winter storms, goes straight into a gap like that. Lifted flashing rarely reseats properly, because the metal has fatigued and the fastener holes have wallowed out. Replacement of the affected section is the honest fix.
4. Counter flashing that's surface-mounted and caulked
Walk around your house and look up. On a properly flashed chimney, the top edge of the metal disappears into a mortar joint. On a shortcut install, you'll see the metal sitting flat against the brick with a bead of caulk along the top. That caulk is the only thing keeping water out, and caulk in the San Gabriel Valley sun lasts a few years at best. If your chimney was flashed this way — common on quick flips and budget re-roofs — plan on replacement done correctly rather than a third round of caulk.
5. Sealant that cracks again within a year or two
Related to the above: if you've resealed and the cracks return quickly, the joint is moving more than sealant can handle, or the sealant is being asked to bridge a gap that metal should be covering. Repeated fast failure is the flashing telling you the problem is geometry, not glue.
6. The flashing is simply old
Galvanized flashing typically serves 20–30 years. If your home still has its original flashing from a 1990s or earlier roof — and plenty of Covina's 1950s–70s homes have been re-roofed around old flashing rather than having it replaced — age alone is a reasonable argument for replacement during the next roof or repair project, before it starts leaking instead of after.
7. Damage around the chimney: curled shingles, soft decking, moss
Shingles near the chimney that curl, crack, or lose granules faster than the rest of the roof; a spongy feel to the decking; moss or algae that only grows in the chimney's shadow line. These say water has been lingering at the joint for a long time. Long-running moisture usually means the flashing system has been bypassed for a while — and the repair scope may include decking, which is another reason to address it sooner than later.
Repair vs. Replacement: The Quick Test
Ask three questions:
- Is the metal itself intact? No rust-through, no perforation → repair may be enough.
- Was it installed correctly? Stepped into the shingles, counter flashing cut into the mortar → repair may be enough.
- Has it been patched more than once? Twice-patched flashing that still leaks is telling you something. Listen to it.
Two or more "wrong" answers and replacement is almost always the better money. Our chimney flashing replacement page explains how a proper replacement is built, and the guide to what flashing replacement costs covers what each route typically runs — reseals at $250–$500 versus full replacements at $900–$1,800+.
What to Do This Week
You don't need a ladder for the first check. Binoculars from the driveway will show you rust streaks, lifted edges, and surface-mounted counter flashing. Inside, photograph your ceiling stain with a coin next to it for scale, then photograph it again after the next rain — growth between photos is hard evidence the leak is active.
Then get it looked at before the season turns. October in Covina is the last easy month: after the first big November storm, every chimney crew in the valley is booked, and a stain becomes a drip becomes damaged decking.
FlashGuard Chimney Flashing Repair — 440 N Barranca Ave, Covina, CA 91723. Call (626) 479-5904 for an inspection. We'll show you photos of your own flashing and tell you plainly whether it needs a $300 repair or a replacement — and if a repair will honestly do, that's what we'll quote.
Frequently Asked Questions
How long does chimney flashing last? Galvanized steel flashing typically lasts 20–30 years; stainless steel longer, and copper longest of all — often the life of the roof. Lifespan drops sharply when sealant is relied on as the primary waterproofing instead of properly lapped and cut-in metal.
Can rusted chimney flashing be repaired? Surface rust can sometimes be cleaned, treated, and sealed if the metal underneath is still solid. Rusted-through flashing cannot be reliably repaired — coatings bridge the hole temporarily, but the metal continues to corrode beneath them. Perforated sections need replacement.
Will a roofer replace flashing during a re-roof? They should — a re-roof is the cheapest moment to replace flashing, because the shingles are already off. But some re-roof quotes reuse old flashing to stay low. Ask explicitly whether new step and counter flashing is included, and get the answer in writing.
Does a flashing replacement require removing shingles? Yes, the shingles around the chimney are lifted or removed to install step flashing correctly, then re-laid or replaced. On tile roofs, the tiles around the chimney are carefully removed and reset. This is skilled work — it's why flashing replacement is a day job rather than an hour job.