Helpful Chimney Vocabulary

Click on any word below for a simple understanding of words most commonly used. Please contact us if there is some word you do not find on the list but need help understanding.

Chimney Diagrams

Glossary

Anchor

Anchors are straps of steel that are secured into the bond beam and are tied back to the floor joists, roof rafters or wall members. The anchors tie the chimney to the house, which may provide support in the event of wind or earthquake.

(Also known as an FHA Strap or Anchor Tie.)

Anchor Tie

Anchors are straps of steel that are secured into the bond beam and are tied back to the floor joists, roof rafters or wall members. The anchors tie the chimney to the house, which may provide support in the event of wind or earthquake.

(Also known as an FHA Strap or Anchor Tie.)

Approved

Acceptable to the authority having jurisdiction.
Ash

The solid residue that remains after combustion is complete.
Ash Dump

The trap door on the floor of the inner hearth that leads to the ash pit.
Ash Pit

A space into which the ashes are dumped. It is a non-combustible storage compartment behind or below the firebox, which helps keep the fireplace clean without having to carry ashes through the house.
Baffle

An object installed in an appliance to change the direction of, or retard airflow, air-fuel mixtures, or flue gases.
Bond

Where referring to bricklaying and masonry chimneys, that connection between brick, stone or other masonry units formed by lapping them upon one another in carrying up the work, thereby forming an inseparable mass.
Bond Beam

A member poured in the masonry at the support level of the chimney. The support level is usually at the floor and at the ceiling or roofline. It may also be above the roofline if the chimney is tall enough to require a supplementary support.
BTU

Abbreviation for British Thermal Unit. The quantity of heat needed to raise the temperature of 1 pound of water 1°F.
Chase Cover

A chase is the chimney framework of either wood or metal studs. The chase cover is a galvanized sheet of metal fit to cover the chase and overhang the sides by 1/2-3/4”. Allowance of an inch air gap between the storm collar and the chase cover along with a 3/8” air space between the frame and cover established by spacers.

chasepic
Chimney

A structure containing one or more vertical or nearly vertical passageways for conveying flue gases to the outside atmosphere.
Chimney Cap

A protective covering or housing for the top of a chimney intended to prevent the entry of rain, snow, animals, birds as well as downdrafts.

(Also known as a Rain Cap.)

chimney-cap
Combustible Material

Material made of or surfaced with wood, compressed paper, plat fibers, plastic, or other material that can ignite and burn, whether flame-proofed or not, or whether plastered or unplastered.
Corbel

Units of masonry projecting from or projecting upward and outward from the face of a wall or chimney in courses to form a support or ledge for a beam, rafter, or other member.

corbel
Creosote

A natural by-product of burning wood. It can be defined as a combustible deposit, which originates as condensed wood smoke, including tar, vapors and other organic compounds. The physical appearance of these creosote deposits is usually dark brown or black in color and watery or tar-like depending on the mixture of tar and vapors and the amount of water vapor condensing.

In contrast with creosote, soot deposits are soft and black or brown in color, often mixed with fly ash.

Cricket

A simple description is a ridge that extends from the back of the chimney to the slope of the roof. Usually found on chimneys wider than 30” with the purpose of shedding water away from the connection between the chimney and roof.

(Also known as a Saddle.)

cricket
Crown

The slight slope or beveled edge on the top surface of a chimney designed to shed water away from the flue liner.

(Also known as the Wash.)

wash
CSIA

Chimney Safety Institute of America – CSIA is a non-profit, tax-exempt educational institution dedicated to chimney and venting system safety. CSIA is committed to the elimination of residential chimney fires, carbon monoxide intrusion and other chimney-related hazards that result in the loss of lives and property. To achieve its goals, CSIA devotes its resources to educating the public, chimney service professionals and other fire prevention specialists about the prevention and correction of chimney and venting system hazards.

csiacert
Damper

A valve or plate for controlling draft or the flow of gases, including air.

damper
Draft

The pressure differential that causes the flow of air or gases through a chimney, gas vent, or venting system.
Factory-Built Appliance

A manufactured appliance furnished by the manufacturer as a single assembly or as a package set of subassemblies or parts, and including all the essential components necessary for it to function normally where installed as intended.
Factory-Built Chimney

A chimney suitable for continuous use at 1000°F (538°C), composed of listed, factory-built components that might be fully enclosed in combustible, residential-type construction, and that is assembled in accordance with the terms of the listing to form the completed chimney.

factory-built
FHA Strap

Anchors are straps of steel that are secured into the bond beam and are tied back to the floor joists, roof rafters or wall members. The anchors tie the chimney to the house, which may provide support in the event of wind or earthquake.

(Also known as an FHA Strap or Anchor Tie.)

Firestop

Horizontal or vertical barriers intended to retard the spread of fire and hot gases between concealed areas. Firestopping shall be provided to cut off all concealed draft openings (both vertical and horizontal), and form an effective barrier between stories, and between a top story and roof space.

firestop
Flashing

Sheet metal between the chimney and the roof, embedded into the chimney and under the roofing material to prevent rain from leaking between the roof and the chimney.

flashing
Flue

The general term for a passage through which gases are conveyed from the combustion chamber to the outer air.
Hearth

The floor area within the fire chamber of a fireplace or a fireplace stove.
Hearth Extension

The noncombustible surfacing applied to the floor area extending in front of and at the sides of the hearth opening of a fireplace or a fireplace stove. Also where applied to the floor area beneath a fireplace stove or beneath an elevated overhanging fireplace hearth.

hearth-extension
Histoplasmosis

A fungal infection of the lungs caused by breathing in dust from soil enriched by bird dung (i.e. soil from chicken coups or fireplace smoke shelves).
Lintel

Where referring to masonry fireplaces, that horizontal, noncombustible member, usually of masonry or steal, spanning the opening of a masonry fireplace to support the load above.

lintel
Listed

Equipment, materials, or services included in a list published by an organization acceptable to the authority having jurisdiction and concerned with evaluation of products or services that maintains periodic inspection of production of listed equipment or materials or periodic evaluation of services and whose listing states either that the equipment, material, or service meets identified standards or has been tested and found suitable for specified purpose.
Mantel

A shelf or facing ornament above a fireplace opening.
Manufacturer

The company or organization that evidences its responsibility by affixing its name or nationally registered trademark or trade name to the appliance concerned.
Masonry Chimney

A field-constructed chimney of solid masonry units, bricks, stones, listed masonry chimney units, or reinforced Portland cement concrete that is lined with suitable chimney flue liners.
NFPA

National Fire Protection Association
Noncombustible Material

A material that, in the form in which it is used and under the conditions anticipated, does not ignite, burn, support combustion, or release flammable vapors when subjected to fire or heat.
Parging

A coat of mortar applied to the inside of a masonry chimney or to the walls of a smoke chamber.
Pyrolysis

Chemical alteration of wood, coal, or other combustible materials as a result of the application of heat.
Rain Cap

A protective covering or housing for the top of a chimney intended to prevent the entry of rain, snow, animals, birds as well as downdrafts.

(Also known as a Rain Cap.)

rain-cap
Saddle

A simple description is a ridge that extends from the back of the chimney to the slope of the roof. Usually found on chimneys wider than 30” with the purpose of shedding water away from the connection between the chimney and roof.

(Also known as a Saddle.)

saddle
Shroud

Decorative structures commonly designed by architects and installed around the top of the chimney. Typically made from sheet metal or terra cotta materials, and often supported by plywood structures. Their purpose is aesthetics, not functional. Shrouds may cause heat to transfer to the wood frame of a chimney chase, allow heat and smoke to affect the thermo siphoning system (cooling) or potentially affect the draw of the system.

shroud
Smoke Chamber

The transitional area from the damper opening to the beginning of the flue liner in a fireplace system.

The smoke chamber acts as a funnel to compress the smoke and gases from the fire so that they will squeeze into the chimney flue above. The smoke chamber is important for good draft action. It should be symmetrical in shape so that the draft pulls evenly on the fire in the firebox. The smoke chamber should be centered with the flue directly above the fireplace and its walls should be sloped at the same angle to provide even draft from the firebox to the chimney.

smoke-chamber
Smoke Shelf

A smoke shelf is located at the bottom of the smoke chamber behind the damper and can collect soot and also gather any rain water that runs down the chimney. A smoke shelf improves draft conditions in a chimney and help eliminates downdrafts.

smoke-shelf
Smoke Test

A procedure for ascertaining the tightness of a chimney and for detecting any cracks in a masonry chimney flue or deterioration or breaks in the integrity of a factory-built or metal chimney flue. The procedure involves igniting a smoke bomb or building a smoky fire in a fireplace or solid fuel-burning appliance, covering the chimney termination and checking for smoke leakage through the chimney walls.
Solid Fuel

Wood, coal and other similar organic materials and any combination of them.
Spark Arrester

Screening material or a screening device attached to a chimney termination to prevent the passage of sparks and brands to the outside atmosphere.

spark-arrester
Unlisted Metal Chimney

A manufactured or field-constructed chimney intended only for non-residential applications having one or more metal walls, or made of metal with a refractory lining, and that is capable of withstanding the flue gas conditions of its use.
Wash

The slight slope or beveled edge on the top surface of a chimney designed to shed water away from the flue liner.

(Also known as the Crown.)

wash
Wythe

Where referring to masonry chimneys, a course, a thinness, or a continuous vertical section of masonry separating flues in a chimney.