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Fix a chimney flashing that leaks

We'll confirm the leak is at the chimney flashing, inspect the step flashing and base flashing for gaps or rust, then reseal or tell you when to call a roofer.

Troubleshooting · Home maintenance
1–2 hours
What you'll need
  • Roofing cement or flashing sealant
  • Ladder (sturdy, with spotter)
  • Putty knife or trowel
  • Wire brush (for cleaning)
Step 1 of 6

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Steps

Goal: Confirm the leak is at the chimney flashing, inspect the step flashing and base flashing, then reseal or call a roofer when needed.

  • Check where water appears—attic near the chimney, ceiling below, or inside the fireplace. Water during or right after rain points to the chimney or roof.
  • Good: Water or stains correlate with rain. Proceed to Inspect flashing.
  • Bad: Water appears without rain—may be condensation or a different source. See When to get help.

Inspect flashing

Goal: Check the step flashing, base flashing, and counter flashing for gaps or rust.

  • From the roof (use a sturdy ladder and have a spotter), inspect the step flashing where the chimney meets the roof. Look for rust, gaps between pieces, or loose metal.
  • Check the base flashing—the flat metal at the bottom of the chimney. Look for pulled-away edges or gaps where it meets the roof.
  • Inspect the counter flashing—the metal on the chimney brick that overlaps the step flashing. Look for gaps or loose mortar.
  • Good: You see the flashing condition. Proceed to Reseal path if small gaps or rust spots.
  • Bad: Flashing is severely rusted, bent, or missing sections—call a roofer.

Reseal path

Goal: Reseal small gaps in the chimney flashing with roofing cement or flashing sealant.

  • Clean the area with a wire brush. Apply roofing cement or flashing sealant to seal gaps. Spread it to cover the joint and overlap onto sound metal.
  • Tuck base flashing under shingles if it has pulled away. Seal the exposed edges.
  • Good: Gaps are sealed. Test after rain.
  • Bad: Damage is severe—call a roofer for flashing replacement.

When to get help

Call a roofer if:

  • The flashing is severely damaged, rusted through, or needs replacement.
  • You are not comfortable working on the roof.

Roof work is hazardous. Do not risk a fall.

Verification

  • No new water entry in the attic, ceiling, or fireplace during or after rain.
  • Flashing is sealed with no visible gaps at the roof-chimney joint.
  • Base flashing is tucked under shingles; counter flashing has no gaps.

Escalation ladder

Work from the device outward. Stop when the problem is fixed.

  1. Confirm leak source Verify water enters during rain; note where it appears (attic, ceiling, fireplace).
  2. Inspect flashing Check step flashing, base flashing, and counter flashing for gaps or rust.
  3. Reseal Clean and apply roofing cement or flashing sealant to close gaps.
  4. Call a roofer Severely damaged flashing or unsafe access—call a roofer.

What to capture if you need help

Before calling support or posting for help, have these ready. It speeds everything up.

  • Where water appears (attic, ceiling, fireplace)
  • Step flashing condition (gaps, rust, loose)
  • Base flashing condition (pulled away, gaps)
  • Counter flashing condition
  • Steps already tried

Does the leak correlate with the chimney flashing and rain?

Trace the leak upward. Chimney flashing is where the chimney meets the roof. Confirm the leak appears during or after rain.

Note where water appears. Trace it upward to the roof. Chimney and rain: proceed to inspect flashing. Not chimney or not rain: may be different source—see fix-roof-leaks.

Yes No

You can change your answer later.

May not be chimney flashing leak

If the leak does not correlate with the chimney or rain, the source may be elsewhere—check gutters, valleys, or other roof areas. See fix-roof-leaks for general leak tracing.

Done

Can you safely access the roof?

Chimney flashing inspection and repair require roof access.

Check roof pitch and height. Safe access: proceed to inspect. Steep or high: call a roofer.

Yes No

You can change your answer later.

Is the flashing damaged or has gaps?

Step flashing, base flashing, and counter flashing seal the roof-chimney joint. Gaps, rust, or loose metal let water in.

Inspect the step flashing, base flashing, and counter flashing. Look for gaps, rust, loose metal, or pulled-away edges. Gaps or minor rust: reseal with roofing cement or flashing sealant. Severely rusted or missing: call a roofer.

Yes No (leak continues)

You can change your answer later.

Reseal flashing and test

Clean the area and apply roofing cement or flashing sealant to close gaps. Tuck base flashing under shingles if it pulled away. Test with rain or hose. If water still enters, the damage may be beyond DIY—call a roofer.

Done

Call a roofer

Call a roofer if: the flashing is severely damaged or rusted through, you need to replace step flashing, or you are not comfortable working on the roof. Roof work is hazardous—do not risk a fall.

Done

Reviewed by Blackbox Atlas

Frequently asked questions

Why does chimney flashing leak?
Flashing seals the joint where the chimney meets the roof. Common causes: sealant fails with age, step flashing rusts or separates, base flashing pulls away from shingles, or the installation was never done correctly. Water follows the path of least resistance—often the flashing first.
Can I fix chimney flashing leaks myself?
Yes, for minor issues: resealing gaps with roofing cement or flashing sealant, tucking base flashing back under shingles. If the flashing is severely rusted, bent, or missing sections, call a roofer for replacement.
When should I call a roofer for chimney flashing?
Call a roofer if the flashing is severely rusted, bent, or missing sections; if you need to replace step flashing; or if you are not comfortable working on the roof. Roof work is hazardous—do not risk a fall.

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