Chimney basics
Parts of a chimney, from firebox to cap
Each part of a chimney has one job. Knowing the jobs helps you understand what an inspector is describing.
Short answer. From bottom to top: firebox, damper, smoke chamber, flue, then the crown, cap and flashing that protect the top. Most wear shows up at the top, where weather hits hardest, and in the flue, where deposits and heat do their work.
The table at a glance
| Part | What it does | What commonly wears |
|---|---|---|
| Firebox | Holds the fire; walls take the heat | Cracked panels and joints |
| Damper | Opens and closes the flue | Rust, warping, sticking |
| Smoke chamber | Funnels smoke into the flue | Rough or cracked surfaces |
| Flue and liner | Carries gases up and out | Cracks, deposits, corrosion |
| Chimney crown | Sheds water off the top of the masonry | Cracks and crumbling |
| Cap | Keeps rain and animals out of the flue | Rust, loose or missing |
| Flashing | Seals the chimney where it meets the roof | Gaps and failed sealant |
Inside the house
The firebox is lined to resist heat, but repeated fires crack its panels and mortar. The damper sits just above it. Older steel dampers rust and warp. Above the damper is the smoke chamber, which is explained in its own guide.
Inside the chimney
The flue is the passage itself. In many older chimneys it is clay tile. A liner is a separate sleeve, often stainless steel, placed in the flue. The difference is covered in Flue vs. liner.
At the top
The crown is the slab around the flue. The cap covers the flue opening. Flashing is the metal that seals the joint between chimney and roof. Water that gets past any of these three ends up in the masonry. See Chimney cap vs. chase cover for the difference between two similar-sounding parts.
Where problems usually start
| Part | Common issue | Related guide |
|---|---|---|
| Crown | Cracks letting water in | Why is my chimney crown cracked? |
| Cap | Missing, loose or rusted | Chimney cap vs. chase cover vs. crown |
| Flashing | Gaps where chimney meets roof | Chimney flashing and crickets |
| Brick and mortar | Eroded joints, spalling | Repointing or rebuilding a chimney? |
| Liner | Cracked or missing tile | Do you need a chimney liner? |
| Smoke chamber | Rough or deteriorated surfaces | The smoke chamber, explained |
| Damper | Stuck or leaking | Damper not working: causes and options |
About this guide. Published by Dr. Sweeper as general homeowner education, last updated October 1, 2026. Sources are linked where they are cited. What applies to your home can depend on your local building code, your appliance and its manufacturer's instructions, and the actual condition of your chimney, so this guide is not a substitute for an inspection.
If you need help
Related services
Chimney inspection
A condition check of the chimney system.
Learn moreCrown repair
Repair of the cement or masonry top of the chimney.
Learn moreChimney caps
Rain and animal protection at the flue top.
Learn moreCap Replacement
Rusted, bent or missing caps.
Learn moreDamper Replacement
Warped or rusted dampers.
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