Chimneys are one of the most common leak locations on a roof—because they combine multiple failure points: masonry, metal, fasteners, and a big interruption in the shingle pattern.
If your chimney leak “goes away” after someone adds caulk, it usually comes back. Durable chimney repairs rebuild the flashing system instead of relying on sealant alone.
The 4 most common chimney leak causes
- Step flashing failure: missing, short, or incorrectly lapped pieces along the sides.
- Counter flashing issues: not embedded into masonry, loose from mortar, or missing entirely.
- Back-pan / cricket problems: water pooling behind a wide chimney.
- Masonry deterioration: cracked mortar joints or a failing chimney cap letting water in.
What a correct chimney flashing system looks like
- Step flashing: individual pieces woven with each shingle course.
- Counter flashing: covers the top of step flashing and is mechanically tied into the chimney.
- Back-pan: directs water around the uphill side of the chimney.
- Cricket (when appropriate): a small peaked diverter behind the chimney to split water flow.
Why caulk fails
Sealants degrade from UV exposure and movement. If the metal layers are wrong or incomplete, sealant can’t fix the underlying water path.
Homeowner signs of a chimney flashing problem
- Stains on the ceiling near the chimney chase
- Water in the firebox after storms
- Wet framing or stained sheathing in the attic near the chimney
- Rust or gaps visible where flashing meets masonry
Next step
If you suspect chimney flashing, compare what you see to our broader roof flashing guide and then schedule a documented inspection. We can often rebuild chimney flashing as a targeted repair when the surrounding roof is still in good condition. To book, request an estimate.