How the Parts Contribute to the Whole.
Understanding the parts of a chimney helps to respect the importance of inspections and annual maintenance.
Above the Roof
Flue Liner is a conduit inside of the chimney that is made from clay, ceramic or metal material. It has three important purposes: Heat Transfer, Protect the Masonry, Maximum Efficiency.
A common sign you need a chimney liner replaced is when you notice that your chimney walls are deteriorating at a faster pace than normal. When it is not in proper working condition, the heat will damage your brick and mortar quicker.
Crown/ Wash is a large slab or masonry coating that covers the top opening of the brick, block, stone or stucco chimney. Unlike a chimney cap, which is typically made of metal and covers the opening to the flue, the crown/wash covers the entire top of the chimney.
Chimney Walls must be a minimum of 4 inches of solid masonry completely surrounding the flue liner. The flue lining extends the entire length of the chimney.
Behind the Wall
Chimney Flue is constructed directly over the fireplace. It is a duct, pipe or opening in a chimney for conveying exhaust gases from a fireplace, furnace, water heater, boiler or generator to the outdoors. A flue liner also protects the chimney walls from heat and corrosion.
The Throat is the top of the firebox below and at the damper. The Smoke Shelf is the area behind the damper and at the bottom of the chimney that is nearly level. The Smoke Chamber is the sloping section of the fireplace above the damper and throat, but below the chimney flue.
They all work together to take the exhaust gases from the large firebox and direct them into the relatively small chimney flue. The goal is to gently compress the exhaust gases without creating a backdraft. If it works well, they accelerate the exhaust gases up into the chimney and help promote good draft. If it is damaged or not working efficiently, the homeowner can end up with smoke in the house.
The Throat Damper is positioned just inside the base of the chimney and at the top of the fireplace. The position allows the damper to be hidden from view but also easily accessible from within the fireplace. It controls how quickly warm air, waste gases and smoke are released from the fireplace during a fire, while also helping to reduce the inflow of cold air from the outside while the fireplace isn’t in use.
The Lintel supports the chimney above the fireplace. It takes loads coming from the above wall and transfer its load to the side walls. A lintel beam generally ends into the masonry wall so as to convey the weight carried by them to the masonry walls and its width the same to the wall width.
The fireplace Mantel (also known as a chimneypiece) originated as a hood that projected over a fire grate to catch the smoke. Today this decorative framework comes in a variety of styles and sizes accessorizing the fireplace.
The Firebox is the structure that contains the fire and holds your wood or gas fuel. It is just like a box but it doesn’t include the fuel source like a gas log set or burner. All fireplaces including gas, wood-burning and pellet contain a firebox.
A Hearth is the noncombustible floor of your fireplace. The word “hearth” is also referred to as the firebox, the raised area around the fireplace and even the whole fireplace, mantel, hearth extension and chimney. A Hearth Extension is the noncombustible material in front of and at the sides of a fireplace opening. Both are designed to prevent sparks from leaving the fireplace and igniting nearby combustibles.
Below the Foundation
The Clean Out Door helps with cleaning the Ash Dump which is located in the middle of the firebox and makes it easy to remove ash from the firebox. When burning, the ashes are pushed to the grate at the back of the fireplace and fall down into the Ash Pit which is where the dumped ash collects. The Ash Pit should be emptied frequently, not just during a chimney sweep cleaning, to help prevent hazardous accumulation of flammable byproducts.
The Foundation provides structural support for the chimney and is specially constructed to withstand heat from hot ash. The horizontal surface under the Ash Pit and Foundation is the Footing, usually located in the basement.