Chimney and fireplace parts, in the words a written estimate uses

Why the names on an estimate matter

Chimney anatomy diagrams name the parts one way, and two contractors can look at the same chimney and use different words. The clearest example sits at the top. The Florida Building Code calls the concrete, metal or stone top of a masonry chimney its cap. Many estimates call that same slab the crown, and keep the word cap for the metal cover with a screen over the flue.

So read each line for the part it describes as well as the label. If an estimate says cap replacement, ask whether it means the metal cover or the masonry top. The difference is a small part versus a masonry job. The sections below run from the floor to the roof, with the jobs each part usually shows up in.

Hearth lines on the estimate

BIA's fireplace design note splits the hearth in two. The inner hearth is the floor of the firebox, where the fire sits. The hearth extension is the noncombustible surface in front of the opening that catches sparks and rolling embers. Under the building code, both must be concrete or masonry, supported by noncombustible materials.

Hearth lines on an estimate usually cover cracked or loose tile, brick or stone on the extension. Others cover an extension too small for the opening, or a hearth that has settled. On a factory-built fireplace, the hearth extension follows the fireplace's listing instead.

Firebox, firebrick and lintel lines

The firebox is the chamber that holds the fire. In a masonry fireplace, the code sets the firebox wall thickness, and a firebrick lining must be laid in refractory mortar made for high heat. Above the opening, a noncombustible lintel carries the masonry over it. A factory-built fireplace uses a metal firebox, often lined with molded refractory panels rather than loose brick.

Firebox lines cover replacing cracked or missing firebrick, repointing its joints with refractory mortar, or rebuilding a firebox wall. On a factory-built unit, the same line may read panel replacement, and the panels should be the fireplace maker's own parts. Estimates for fireplace repair often group these items together.

Throat, damper and smoke shelf lines

BIA describes the throat as the slot-like opening just above the firebox where flames and smoke pass upward. The damper usually sits there, as a metal plate the code requires to be worked from the room. A top-mounted damper at the chimney top does the same job from the other end. Some masonry fireplaces also have a smoke shelf behind the damper, though BIA notes that some designs, such as the Rumford, leave it out.

Damper lines cover freeing, repairing or replacing a throat damper, fitting a clamp that holds it open for gas logs, or installing a top damper instead. Ask which damper the line means and how it will be worked.

Smoke chamber parging and repair lines

The smoke chamber is the sloped space above the damper that funnels smoke into the flue. BIA notes that it also carries the flue above it. The code requires its inside surface to be parged smooth with refractory mortar, which BIA explains reduces friction and keeps smoke from leaking.

A smoke chamber line usually means parging the walls smooth, filling gaps, or repairing a chamber that has cracked. Because it sits out of sight, ask the estimate to say what was found there and how the work will reach it.

Flue and liner lines

The flue is the passage that carries smoke from the smoke chamber to the top of the chimney. The code requires masonry chimneys to be lined. The lining may be clay flue tile, a listed chimney lining system, or another approved material. A flue that serves a gas appliance or an insert follows that appliance's listing.

Flue lines on an estimate cover repairing damaged tile joints, relining with a listed stainless liner, or removing heavy deposits before either. A relining line should name the liner, its size, and what connects to it at each end.

Chimney wall and finish lines

The chimney walls are the masonry that encloses the flue. They may be brick, block or stone, and some are finished in stucco. Mortar joints hold the units together and wear with the weather over time.

Wall lines cover repointing worn joints, replacing damaged brick, or repairing stucco. The line should say how much of the wall is included, whether the work matches the existing mortar or finish, and whether any water entry was traced before the repair.

Crown, cap and spark screen lines at the top

The masonry top, whatever the estimate calls it, is the slab that covers the chimney walls around the flue. The code asks for it to be sloped to shed water, with a drip edge and a bond break around the flue liner. BIA's chimney note recommends a prefabricated cap and cautions that a mortar wash may not be as durable.

The metal cap over the flue keeps rain, leaves and animals out, and its screen can serve as a spark arrestor. The code requires a spark arrestor screen to be removable so the flue can still be cleaned. Lines at the top cover crown repair or rebuilding, a sealer on the masonry top, or cap replacement. Check that each line says which of the two it means.

Flashing and cricket lines at the roof

Flashing is the sheet metal that closes the joint between the chimney and the roof. BIA's chimney note describes two layers. Base flashing runs along the roof, and counter flashing is set into the mortar joints and laps over it. A cricket is a small peaked section on the uphill side of a wide chimney that sends water around it. The code requires one where a chimney is wider than a set limit and does not meet the ridge.

Flashing lines cover resealing, replacing or rebuilding the flashing. On a tile or flat roof, part of that work touches the roof covering. The estimate should say who handles the roof side and how the two trades hand off.

Factory-built systems have their own list

Factory-built fireplaces come with a different set of parts, all made and listed to work together. The code requires the fireplace and its chimney to be listed and labeled and installed as the manufacturer instructs. UL 103 covers factory-built chimneys for residential appliances.

Expect these names on an estimate for a factory-built system.

• Listed chimney pipe, the round metal sections of the flue
• Firestop spacers, where the pipe passes through a ceiling or floor
• An attic insulation shield, where the pipe crosses insulation
• The chase, the framed enclosure around the pipe outside
• The chase top or chase cover, the metal lid over that enclosure
• The termination cap, the listed cap that ends the chimney above the roof
• Refractory panels, doors, screens and grates, each by the maker's part number

Reading your estimate line by line

Each line should name the part, the finding and the work, and say what is left out. Where a factory-built part is replaced, the line should name the maker's part. Where masonry is repaired, it should say the extent. If two lines seem to describe one part, ask before you approve.

After a free inspection, the estimate we write uses these terms, with upfront pricing and no hidden fees. You approve each item before we start, and the finished work is written up in the same terms. For work on the masonry itself, the estimate falls under chimney repair. For factory-built units, it falls under prefab fireplace repair.

Sources

• 2023 Florida Building Code, Residential, chapter 10: Code names and roles for the hearth, firebox, lintel, damper, smoke chamber, lining, cap, spark arrestor, cricket and factory-built systems.
• BIA Technical Note 19, Residential Fireplace Design: The parts of a masonry fireplace, including the throat, damper, smoke shelf and smoke chamber.
• BIA Technical Note 19B, Residential Chimneys, Design and Construction: The chimney cap detail, flue liners, and base and counter flashing at the roof.
• Superior WCT3000 wood-burning fireplace manual: A factory-built parts list with firestop spacers, listed terminations and the maker's own components.
• UL 103 Factory-Built Chimneys, standard scope: Factory-built chimney pipe for residential appliances, listed as a system of its own.