The parts of a chimney, top to bottom
Read the stack from the top of the roof down to the hearth. Each part sits on the one below it and depends on it.
Above the roofline you also have the flashing, the metal that seals the joint where the chimney passes through the roof. It is the single most common source of chimney leaks, which is why it gets its own section on our chimney repair page.
Chimney care by the numbers
A handful of figures explain most of what a homeowner needs to remember.
The three stages of creosote
Creosote is the tar that wood smoke leaves behind as it cools on the flue wall. It builds in stages, and each stage is harder to remove than the last.
Burning seasoned wood, running a hot fire rather than a smouldering one, and sweeping on schedule keep creosote at Stage 1, where it is cheap and quick to deal with.
How to use this as a homeowner
You do not need to climb on the roof. From the ground you can check the cap is present and the crown is not visibly crumbling; from inside you can open the damper and shine a light up to look for flaking or glaze on the flue wall, and check the firebox mortar joints. Anything beyond that — measuring creosote depth, judging a liner, or reading flashing — is what the camera and training on an inspection are for. Our DIY chimney care guide covers exactly where homeowner checks stop being sensible, and the history of chimneys explains why the design works the way it does.
Frequently Asked Questions
What is the most important part of a chimney?
No single part; they work as a system. If forced to pick, the liner matters most for safety, because a cracked or missing liner lets heat and gases reach the surrounding masonry and framing.
What does the chimney crown do?
The crown is the sloped cap of concrete or mortar at the very top of the masonry. It sheds rain away from the flue and the brickwork. A cracked crown is a leading cause of water damage inside a chimney.
What is the difference between the cap and the crown?
The crown is the masonry wash at the top of the stack. The cap is the metal lid above it that keeps rain, animals and sparks out of the flue opening. A chimney needs both.
What is the smoke chamber?
It is the angled space above the firebox that narrows to funnel smoke into the flue. When it is parged smooth it helps draft; when it is rough or corbelled it can slow smoke and let creosote collect.
How do I know which liner my chimney has?
Older masonry chimneys usually have clay tile, visible as square terracotta sections. Relined chimneys have a round stainless steel pipe. A Level 2 inspection with a camera confirms the type and its condition.
How often should the whole system be looked at?
Once a year, per NFPA 211, regardless of how often you use the fireplace. Annual inspection catches small faults before they become the expensive ones.
Is a little creosote a problem?
A thin film is normal. Once build-up reaches about one eighth of an inch, the CSIA guidance is to sweep, because that is enough fuel to support a chimney fire.
Can I inspect my own chimney?
You can do useful ground-level and firebox checks, described above. You cannot see the full flue, the smoke chamber or the flashing without a camera and roof access, so a yearly professional look is still needed.
Written by Johnathan Mason, owner of Ace Chimney Service, Crystal Lake, IL — 29 years in chimney and fireplace work.
Published: October 3, 2026 · Updated: October 3, 2026
Questions about any part of your chimney? Call Ace Chimney Service at (815) 320-0883 or request an appointment online. See all our chimney services.