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.

Chimney Liner:

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.”


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.


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:

  1. Metal factory-built chimneys
  2. 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



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 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.


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. 



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


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


This is the area just above the firebox.



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

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