Chimney Glossary

The terms a technician uses during an inspection, defined plainly, so you know exactly what you're being told.

Chimney terminology sounds more technical than it needs to be. Here's what the common terms actually mean.

Cap: The cover that sits directly over the flue opening, keeping out rain, snow, and animals while letting smoke escape. See cap installation.
Chase: The enclosure that houses a factory-built chimney's flue pipe, typically built of wood framing and siding rather than masonry.
Chase Cover: The metal cover on top of a chase, sealing out water where the flue pipe exits. Different from a cap, which sits directly on the flue itself. See cap vs. chase cover.
Creosote: A byproduct of burning wood that coats the inside of the flue. It builds up in stages, and heavier stages become a genuine fire hazard. See creosote explained.
Crown: The concrete or masonry cap on top of a masonry chimney, sloped to shed water away from the flue. See crown repair.
Damper: The movable plate inside the flue that opens to let smoke out during a fire and closes to prevent heat loss and drafts when it's not in use.
Draft: The upward airflow that carries smoke out of the chimney. Poor draft is a common cause of smoke entering the room. See draft problems.
Firebox: The interior chamber where the actual fire burns, lined with firebrick or refractory panels designed to withstand direct flame.
Flashing: The metal strips sealing the joint where the chimney meets the roofline, one of the most common actual leak points. See flashing repair.
Flue: The vertical passage inside the chimney that carries smoke and combustion gases up and out of the home.
Liner: The material lining the inside of the flue — typically clay tile in older homes or stainless steel in newer or upgraded chimneys. See liner installation.
Smoke Chamber: The area directly above the firebox where the chimney narrows down into the flue, funneling smoke upward.
Spalling: Brick or mortar breaking apart at the surface, caused by water absorption followed by freeze-thaw expansion. See tuckpointing.
Tuckpointing: The process of removing damaged mortar and repacking the joints with new, color-matched mortar. The standard fix for spalling and mortar deterioration.