Prior to 1796, brick chimneys were built adjacent to, but outside, the exterior wall of the building. Beginning in 1797, “Rumford” style brick chimneys were built inside the building or incorporated into the exterior wall. They became popular in the Victorian period. Regardless of style, if you own and use a fireplace or wood heater it is important that you know the parts of your chimney, why they're there, and how they function.
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The flue is one or more vertical tubes formed by a chimney that provide the upward path for smoke to follow. They usually are lined for safety and ease of maintenance.
Flues are lined to enhance safety, ease of cleaning and performance. Typical materials used for flue liners are terracotta tile, refractory cement, pumice, stainless steel and aluminium.
The firebox, commonly called the fireplace, comprises the inner and outer hearth. The inner hearth is the actual floor of the firebox and the outer hearth is the part in front of the firebox that extends into the interior of the room.
Fireplace Butt Walls
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Butt walls enclose and support the firebox and form the internal walls of the chimney.
The chimney damper consists of two metal plates that close off the flue when the fireplace is not in use. They are opened and closed by a metal lever. The damper does not form an airtight seal, so it is possible to still feel a draft in the chimney when the damper is closed. This represents energy loss that can be prevented through such means as a glass firescreen that can be used to completely block airflow when the fireplace is cold.
Above the damper, at the throat of the chimney, is the smoke chamber. It is designed to collect and discharge smoke rising from the firebox.
Projecting out from the rear butt wall of the smoke chamber is a shelf that curves upward. It is designed to reflect downdrafts that come down through the top of the chimney.
The lintel is an angle iron at the face of the firebox that supports the masonry around the firebox opening.
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The top of a brick chimney is called the crown. The flue liner extends out beyond the crown by several inches.
A chimney cap fits over the flue(s) at the top of the chimney to keep out rain, snow and debris. It often has screen mesh sides to keep birds and other animals from getting in the chimney. The chimney cap also keeps sparks from falling on the roof. Chimney caps usually are made of copper, stainless steel or black steel.
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The chimney flashing sits at the junction of the chimney and the roof to prevent water from entering.
Ash Dump and Ash Pit
Some chimneys, especially in older houses, have an ash pit at the bottom of the chimney, located either outside or in the basement. There is a small door, called the ash dump, on the floor of the firebox that leads to the ash pit. This makes it possible to sweep ashes and soot into the ash pit for later cleanout.