Chimney flashing replacement means removing the old metal where your chimney meets the roof and installing a new, properly layered system: step flashing woven into the shingle courses and counter flashing set into a fresh-cut mortar joint. You need a full re-flash, not another patch, when the metal is rusted through, bent or lifting at the edges, or was installed incorrectly the first time, so no amount of sealant will hold. In the wet Puget Sound climate, failed flashing is one of the most common reasons water tracks down a chimney and into the ceiling below. Replacement rebuilds a watertight seal designed to last for decades.
What chimney flashing replacement covers
Flashing is the metal that bridges the gap between your chimney and the roof deck. A correct system has two parts. Step flashing is a series of L-shaped pieces woven between each course of shingles along the sides of the chimney. Counter flashing is the upper layer, its top edge let into a groove cut in the chimney's mortar joints, folded down to overlap the step flashing so water sheds outward at every seam. Replacement means removing the old, failed metal and installing both layers correctly, cutting a fresh reglet into the masonry, bedding the counter flashing, and sealing the top edge so the joint stays watertight.
This is a different job from patching an otherwise sound seal. If your flashing is basically intact and just needs the mortar joint re-sealed or a lifted edge re-secured, that repair-scope work is covered on our chimney flashing repair page. Replacement is what you need once the metal itself has failed.
Signs you need replacement, not another patch
- Rust or corrosion: once galvanized flashing rusts through, its watershedding is gone and sealant won't restore it.
- Lifting or bent edges: flashing that moves when touched, or edges curling away from the roof, leaves an open path for water at every gap.
- Tar or caulk "repairs": a chimney sealed only with a smear of roofing tar or a bead of caulk, with no counter flashing set into the mortar, was never flashed correctly and will keep leaking.
- Repeat leaks after patching: if the same stain returns after a previous reseal, the metal underneath has likely reached the end of its life.
- Curling or lifting shingles beside the chimney: often a sign the step flashing beneath has shifted or corroded.
What to expect during the job
We start on the roof and in the attic to confirm the flashing is actually the leak source, not the crown, cap, brick, or a separate roof issue. A leak near a chimney is not automatically any one component, so the diagnosis comes first. For a replacement, we carefully remove the old step and counter flashing, install new step flashing interleaved with the surrounding shingles, cut a clean reglet into the mortar joints, set and fasten the new counter flashing, and seal the top edge. Where the chimney is wide or sits low on the slope, water can pool on the up-roof side; in those cases a cricket, a small peaked diverter behind the chimney, may be recommended so water is steered around it. When we finish, the seal is designed to shed water on its own rather than depend on sealant alone.
Why this is a job for a professional
Flashing replacement is roof-access work that combines roofing and masonry: shingles have to be lifted and re-woven without breaking their own weather seal, and a groove has to be cut into the chimney and the metal bedded so both trades stay watertight. Done wrong, a new install leaks as badly as the old one, and the classic DIY mistake, skipping the counter flashing and relying on tar, is exactly what we get called to undo. We don't advise homeowners to get on the roof for this. It calls for the right layering, fasteners, and fall protection.
Why it matters in the Seattle area
Greater Seattle's long wet season and frequent wind-driven rain put constant pressure on every roof seam, and freeze-thaw cycles in colder stretches work at any gap the metal leaves open. Corroded or poorly installed flashing that might limp along in a dry climate leaks steadily here. Because the water often travels before it shows, a small flashing failure can rot roof sheathing, framing, and drywall long before you see a stain. Replacing failed flashing early is far cheaper than repairing the water damage it causes. If you're not sure whether your chimney needs a repair or a full replacement, our services team can inspect it and tell you which the metal actually needs.
Frequently Asked Questions
How long does replacement flashing last compared to the old metal?
A properly installed flashing system, with step and counter flashing correctly layered and the counter flashing set into the mortar, is built to last for decades, often the life of the roof. Failed flashing usually means the original was either low-grade metal, poorly installed, or simply worn out. We can advise on material during an on-site quote.
Can you reuse my existing flashing during a re-roof?
Sometimes, but only if the metal is still sound. If it's rusted, bent, or was installed incorrectly, reusing it defeats the point of a new roof, since the old flashing becomes the weak link. We inspect it on-site and tell you honestly whether it can stay or should be replaced.
Do I need a cricket built when you replace the flashing?
Not always. A cricket, a small peaked diverter behind the chimney, is recommended mainly on wider chimneys or where the chimney sits low on the roof slope so water pools against the up-roof side. Whether yours needs one depends on chimney width and roof pitch, which we assess in person.
Should a roofer or a chimney company replace my flashing?
Flashing sits at the overlap of both trades, which is why homeowners get conflicting answers. We cover which contractor fits which situation in our blog article on choosing a roofer or chimney company for a leak. In short, the counter-flashing-into-masonry portion is chimney work, so it's worth having someone who handles both the metal and the mortar.