Definitions

Learn the lingo of everything chimney and fireplace with definitions provided by Full Service Chimney.

Ash Pit:

The cavity beneath the firebox, used as a receptacle for ashes and accessible via a cleanout door in the basement or crawl space.

Chimney Cap:

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

A flue lining in a masonry chimney is defined as “a clay, ceramic, or metal conduit installed inside of a chimney, intended to contain the combustion products, direct them to the outside atmosphere, and protect the chimney walls from heat and corrosion.”

Crown:

The top cement-like material at the top of the chimney that marries the brickwork with the flue tile and assists in shedding water away from the chimney.

Damper:

The plate or valve that closes the fireplace flue when the fireplace is not in use.

Factory-Built Chimneys:

There are two basic types of factory-built chimneys, also known as prefabricated chimneys:

Metal factory-built chimneys
Modular/masonry factory-built chimneys

Metal factory-built chimneys are factory-made, field-installed components that when used together properly form a complete chimney system.

Modular/masonry factory-built chimneys are composed of factory-made, field-assembled components of pre-cast masonry materials. Both metal and modular/masonry factory-built chimneys should be listed according to Underwriters Laboratory (UL) standards and installed according to manufacturers instructions.

See a Prefab Chimney Chase Cover Installation

Learn about the Different Types of Fireplaces/Chimneys

Firebox:

A firebox is the place where your fire is built. It consists of 3 walls and a floor constructed of firebrick and refractory mortar. This is where the grate is placed.

Fireplace Doors/Spark Screen:

It is recommended that the height and width of the fireplace opening be covered with a screen and/or glass doors. Be mindful of the type of fireplace, though. Doors intended for a masonry fireplace CANNOT be installed on a prefab or factory-built fireplace. This will create a hot spot at the front of the chimney which can result in an unfriendly fire.

Fireplace Inserts:

Woodstove inserts are often installed in fireplaces to increase the amount of heat emitted into the home. It is important to note that fireplace inserts require the special installation of a liner system, as most fireplace flues are not intended to withstand the heat output of a wood-stove insert. Consult a professional, CSIA Certified Chimney Sweep® before purchasing a fireplace insert to assure a proper fit and proper installation of both the insert and its accompanying liner.

Flashing:

Flashing is a thin layer of sheet metal used to protect against rain or moisture. This layer is applied at joints where the chimney meets the roof, shoulder, etc.

Flue:

A chimney flue is the vertical passageway up the inside of your chimney. The damper is often mistakenly called the flue, but the flue is the passageway.

Hearth:

The hearth is the floor area within the fire chamber of a fireplace or a fireplace stove.

Lintel:

The lintel is the horizontal architectural space between the fireplace opening and the damper.

Masonry Chimneys:

Masonry chimneys are hand-built, field assembled chimneys which may be constructed of brick, concrete block, stone, or pre-cast material.

Smoke Chamber:

The smoke chamber is the roughly-triangular space above the throat of the fireplace leading up to the flue. See an example of Smoke Chamber Parging on our Chimney Liner page.

Spalling:

Spalling is a condition of the chimney where the masonry work (brick or stone) begins to flake or peel from the surface.

Throat:

This is the area just above the firebox.

Wythe:

In a masonry chimney, the wythe is a brick wall that partitions one flue from another inside the same chimney.