Chimney Flashing Leak: How to Spot It and What Fixes It

Chimney flashing leak is one of the most common roof leaks, because the joint where a chimney meets the roof is hard to seal and moves with weather. Flashing that is rusted, lifted or sealed only with tar can let water run into the attic and down ceilings near the chimney.

A lasting repair re-builds the flashing in layers and, if needed, repairs the mortar, crown or cricket.

Chimney flashing leak: how flashing works

Flashing is metal layered with the roof so water always runs over it, not under. A chimney usually has several parts.

Part	What it does
Base (apron) flashing	Covers the lower side of the chimney
Step flashing	Overlaps shingles up the sides
Counterflashing (cap flashing)	Set into the mortar joints and overlaps the step flashing
Cricket or saddle	A small peaked ridge behind a wide chimney that sheds water
Chimney crown	The cap on top that sheds water from the flue

Quick facts: chimney flashing leak
Common causes	Rust, lifted metal, failed sealant, cracked mortar, no cricket
Warning signs	Stains on the ceiling near the chimney, damp attic wood, drips in rain
Not always flashing	Crown cracks, porous brick and flue condensation can look similar
Best fix	Rebuild flashing with proper overlap; repair masonry

Signs of a leak

1. Water stains or peeling paint on the ceiling or wall around the chimney.
2. Damp or stained wood and insulation near the chimney in the attic.
3. Rust, gaps or lifting metal where chimney meets roof.
4. Cracked, dried or tar-smeared sealant around the flashing.
5. Crumbling mortar between the bricks.

Is it really the flashing?

Water near a chimney can also come from a cracked crown, porous bricks that absorb rain, a missing chimney cap, or condensation inside the flue. A leak that appears only in heavy, wind-driven rain often points to the masonry. A roofer or mason can test each area with water.

Repairs

• Reseal minor gaps with roofing sealant, as a short-term measure only.
• Replace the flashing with new metal, layered with the shingles, and set the counterflashing into the mortar joints, sealed properly.
• Repoint damaged mortar and fix cracked bricks.
• Repair or replace the crown with a crack-resistant coating or new crown.
• Add a cricket to a wide chimney, so water does not pool behind it.
• Install a chimney cap to keep rain out of the flue.

What a repair visit looks like

A roofer typically checks the attic for the leak path, then inspects the flashing, mortar joints, crown and cap from the roof. They may spray water in stages to find the entry point. For a flashing repair they remove nearby shingles, install new base and step flashing, tuck counterflashing into cut mortar joints, reseal it, and replace the shingles. If the masonry is cracked, a mason repoints or rebuilds that section first. Ask for before-and-after photos of the work.

Why tar alone fails

A thick coat of roofing tar or caulk can hide a leak for a while, but it cracks and peels as the roof and chimney move. A chimney flashing leak repaired only with tar often returns. A proper repair uses the correct metal and overlap.

Temporary measures

Place a bucket under drips, and ask a roofer about a safe temporary cover. Do not climb a wet roof.

Prevention

Inspect annually, clear debris, keep trees trimmed, and check the flashing after major storms. Replace flashing when the roof is replaced.

When to call a professional

Call a roofer, and a mason if the chimney is damaged, for any leak near the chimney. Chimneys are high and awkward work.

Chimney flashing leak: where the water gets in

The flashing is the metal sheet that seals the joint where a chimney meets the roof. Water is kept out by overlapping layers: step flashing along the sides, counter-flashing set into the masonry, and a cap on top. A chimney flashing leak usually starts where one of these layers has lifted, rusted or pulled away from the brick.

Water often runs down the chimney face and enters at the flashing before it shows inside. Look for staining on the wall next to the fireplace, cracked mortar at the joint, and rust streaks on the metal. A roofer can check the flashing, reseal the joints and, if needed, replace the step flashing that is no longer tight.

Look for rust stains, cracked mortar and loose caulk at the base of the chimney, since water often enters through those joints before it reaches the flashing. Note the spot where the stain appears inside the home.

Related reading

• How to Fix a Leaking Skylight: Leak, Condensation or Flashing?
• Roof Inspection After Storm: Safe Checks, Evidence and Next Steps
• Practical Guide: How to Find Where a Roof Is Leaking
• What Is Drip Edge on a Roof? Purpose, Types and When It Is Needed

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