How do you fix a chimney?
Short answer. Fixing a chimney depends on which part failed: cracked crowns are sealed or rebuilt, missing caps replaced, crumbling mortar repointed, spalled bricks replaced, rusted chase covers swapped, leaking flashing rebuilt with step and counterflashing, and damaged flue liners relined. Masons, chimney sweeps and roofers each handle different pieces, so the first step is finding which part is the problem.
Common chimney repairs
- Crown. Hairline cracks get an elastomeric crown sealer. A broken or poorly built crown is rebuilt with an overhang so water drips clear of the brick.
- Cap. A stainless or galvanized cap with mesh keeps out rain and animals, and replacing one is usually straightforward.
- Mortar joints. Repointing grinds out weathered mortar and packs in fresh mortar of a compatible type. Mortar that is too hard can damage older brick.
- Spalled bricks. Bricks with flaking faces are cut out and replaced, and a breathable water repellent helps prevent more.
- Chase cover. On framed chimneys, a rusted flat cover is replaced with a sloped stainless or galvanized cover that sheds water.
- Flashing. New step flashing woven into the shingles, counterflashing cut into the mortar joints, an apron across the front, and a cricket behind wider chimneys.
- Flue liner. Cracked clay tiles or an unlined flue get a stainless steel or cast-in-place liner sized to the appliance.
- Damper. A rusted throat damper can be replaced with a top-sealing damper.
Who fixes what
Masons handle brick, mortar and crowns. Certified sweeps handle flues, liners, caps and dampers. Roofers handle flashing and crickets where the chimney meets the roof. Some companies cover more than one area, but ask for photos of the problem before anyone starts.
Leaning or badly cracked chimneys
A chimney pulling away from the house or showing large structural cracks is a safety issue. Stop using it and have a mason or structural engineer evaluate it. See chimney leaks and crickets and roof flashing explained.