Exterior · Ohio & Michigan
Chimney leaks and repairs
Why chimneys leak and crumble in freeze-thaw climates, which trade fixes what, and the safety signs that mean stop using the fireplace.
2 min read · Updated
Key takeaways
- Most chimney leaks come from flashing, the crown or the cap, not the brick itself.
- Freeze-thaw winters crack crowns and spall brick faster here than in milder climates.
- Have the flue inspected before the heating season. Leaks and fire safety are separate problems.
A chimney is a masonry tower that pokes through the roof and takes the full force of weather. In Ohio and Michigan, water that soaks into brick and mortar freezes and expands, which breaks down damaged masonry winter after winter.
Where chimney leaks come from
- Flashing where the chimney meets the roof: step flashing and counter flashing, plus a cricket (a small peaked section) behind wide chimneys. This is roofer work.
- The crown, the concrete cap on top. Cracks let water straight into the chimney. This is mason or chimney-specialist work.
- Brick and mortar that has spalled (flaked) or lost mortar. Repointing (tuckpointing) and brick replacement are mason work.
- A missing cap, which lets rain and animals into the flue.
Safety signs
- A leaning chimney, or bricks coming loose, can fall. Keep people clear and get a mason or engineer to assess it.
- Smoke entering the room, poor draft or a strong smoky smell while the fireplace or an appliance is running means stop using it until the flue is inspected. Make sure carbon monoxide alarms work.
Fire-safety standards such as NFPA 211 cover chimney inspection and maintenance. Certified chimney sweeps inspect and clean flues.
Who to call
| Problem | Usually |
|---|---|
| Leak at the roof line, rusted or caulked flashing | Roofer |
| Cracked crown, spalling brick, missing mortar | Mason |
| Leaning chimney or loose bricks | Mason, sometimes an engineer |
| Smoke, draft, creosote, cap | Certified chimney sweep |
Try the chimney repair triage to sort your symptoms.
Flashing, crowns and caps explained
- Step flashing is woven into each course of shingles along the sides of the chimney.
- Counter flashing is set into the mortar joints and laps over the step flashing, so water runs down and out instead of behind it.
- The crown is the concrete or mortar slab on top of the chimney. It should slope away from the flue and overhang the brick so water drips clear.
- The cap covers the flue opening to keep out rain, snow and animals.
A roofer usually handles flashing. A mason handles crowns, mortar and brick. A chimney sweep or chimney professional inspects the flue and liner. Our chimney repair triage helps you tell which one you need.
A seasonal chimney checklist for Ohio and Michigan
Fall, before heating season
- Book the annual flue inspection and sweep if you burn wood.
- Look at the crown and cap from the ground with binoculars.
- Test smoke and carbon-monoxide alarms.
Spring, after the freeze-thaw season
- Look for new cracks, loose brick or white staining (efflorescence) on the chimney.
- Check the ceiling and walls around the chimney inside for water stains.
- If the roof leaked near the chimney over winter, get the flashing looked at before summer storms. Our roof repair triage covers what to do in the meantime.
Chimney leaks and repairs: common questions
Why do chimneys leak more after winter?
Water gets into small cracks in the crown, mortar and brick, freezes and expands. Each freeze-thaw cycle opens the cracks a little more, so damage often shows up as leaks or crumbling brick in spring.
Should chimney flashing be replaced with a new roof?
Usually it should at least be inspected and often replaced. Old step and counter flashing that is reused under new shingles is a common source of leaks. Ask each roofer exactly what they will do at the chimney.
How often should a chimney be inspected?
The national chimney standard, NFPA 211, calls for chimneys, fireplaces and vents to be inspected at least once a year. Fall, before the heating season, is the usual time.
What is a chimney cricket?
A small peaked structure on the uphill side of a wide chimney that splits water and snow around it. The model code calls for one on chimneys wider than 30 inches measured parallel to the ridge.
Can I remove a chimney I no longer use?
Often, but it may be structural, it may still vent a furnace or water heater, and removal can need a permit. Have a mason or contractor confirm what the chimney serves before anyone takes it down.
Sources
- NFPA 211, Standard for Chimneys, Fireplaces, Vents, and Solid Fuel-Burning Appliances, National Fire Protection Association. Industry association
- Chimney Safety Institute of America, Chimney Safety Institute of America (CSIA). Industry association
Industry association that certifies chimney sweeps.
General information only. Codes, product instructions and warranties change, and your local building department and the manufacturer have the final word.