A chimney is a stack of parts that each do one job: the cap and crown keep water and animals out, the flue and liner carry smoke and heat up and out, the smoke chamber and damper control the draft, and the firebox holds the fire. Understanding the parts makes it far easier to know what a repair quote means. Here’s the whole system, top to bottom.
From the top down
Chimney cap
The metal cover and screen on top of the flue. It keeps out rain, snow, birds, and squirrels, and its spark arrestor stops embers from reaching your roof. A missing cap is one of the most common sources of chimney problems.
Crown
The sloped concrete or mortar slab at the very top that sheds water away from the flue and brick. A cracked crown funnels water straight into the chimney, so it’s a high-priority repair.
Flue
The vertical passage inside the chimney that carries smoke and combustion gases out of your home. Its size and shape determine how well your fireplace draws.
Liner
The lining of the flue — clay tile in many older chimneys, or stainless steel in relined ones. It contains heat so it can’t reach nearby framing and gives gases a smooth path out. A cracked liner is a fire and carbon monoxide risk.
Smoke chamber & damper
The smoke chamber funnels smoke from the firebox up into the flue. The damper is the movable plate that opens to let smoke out and closes to block drafts when the fireplace is cold.
Firebox
The chamber where the fire actually burns, built from firebrick to withstand high heat. Cracked firebox brick or mortar should be repaired.
Flashing
The metal sealing where the chimney passes through the roof. Failed flashing is a leading cause of leaks that show up as ceiling stains near the chimney.
Why this matters for repairs
When we quote a job, we’ll name these parts: “the crown is cracked,” “you need a new cap,” “the liner should be replaced.” Knowing the anatomy lets you understand exactly what you’re paying for and why it matters for safety. For the parts most prone to failure, see our caps, crowns & liners page.
Frequently asked questions
What are the main parts of a chimney?
From top to bottom: the cap, the crown, the flue, the liner, the smoke chamber and damper, the firebox, and the flashing where it meets the roof. Each part has a specific safety job, and a failure in any one can cause leaks, poor draft, or fire risk.
What does the chimney crown do?
The crown is the sloped slab at the top that sheds rainwater away from the flue and brick. When it cracks, water pours into the chimney and causes spalling and interior damage, which is why crown repair is one of the most valuable fixes.
What’s the difference between the flue and the liner?
The flue is the passage that smoke travels up; the liner is the material lining that passage. The liner contains heat and gases safely. You can think of the flue as the tunnel and the liner as the protective wall of that tunnel.
What is the damper and where is it?
The damper is a movable metal plate, usually just above the firebox or at the top of the flue, that opens to vent smoke and closes to block drafts when the fireplace is cold. A stuck or warped damper should be repaired.
Why is the chimney cap so important?
The cap keeps rain, snow, animals, and debris out of the flue and stops embers from landing on your roof. Because it prevents water intrusion and blockages at low cost, a good cap is one of the best protections for the whole chimney.
What is flashing and why does it leak?
Flashing is the metal that seals the joint where the chimney passes through the roof. Over time it loosens, corrodes, or pulls away, letting water in. Leaks that show as ceiling stains near the chimney often trace to failed flashing.
What is the firebox made of?
The firebox is built from firebrick and refractory mortar designed to withstand very high heat. Cracks in the firebrick or crumbling mortar joints should be repaired, since they can let heat reach materials behind the firebox.
Which chimney parts fail most often?
The cap, crown, liner, and flashing are the most common failure points, largely because they bear the brunt of water and weather. Catching problems in these parts early is the key to avoiding bigger masonry repairs.
Not sure which part is failing?
Send us what you’re seeing and we’ll tell you which part it is — and whether it’s urgent. 7 days a week.
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Published November 10, 2026 · Written and reviewed by Joseph Ino, Founder & Master Chimney Technician, Chimney Sweep Squad