The Anatomy of a Chimney
When you think of a chimney, chances are you automatically think of a fireplace as well. While these components are the two most common elements of a chimney system, a chimney is actually comprised of several different components – and each contributes to the quality and safety of the system as a whole.
- Foundation: The foundation of a chimney is usually located in the basement. It is typically rectangular, made of brick or stone, and it is responsible for supporting the entire structure, from the ash dump above it to the mortar crown capping the very top. To build a chimney in Wellesley, you must begin with a solid foundation, because from top to bottom, completed structures weigh in between 6 to 7 tons.
- Ash Dump: The ash dump is a holding box that sits directly upon the foundation. It is also located in the basement, just below the actual fireplace. As the ashes from your fire fall away, they are deposited into the dump through a vented opening in the floor of your hearth.
- Hearth: The hearth is the floor of your fireplace, and it usually extends into the room in which the fireplace is located.
- Firebox: This is literally the location where you will build and burn your fires. It is built using firebrick and refractory mortar, which is a specialty mortar developed to withstand high temperatures.
- Lintel: The lintel is heavy piece of angled iron or masonry that sits at the top of the firebox. It supports the inner wall of the chimney, as it begins to extend upward from the fireplace.
- Damper: The damper is a pivoting metal plate located at the “throat” of your chimney. It controls the flow of air and smoke.
- Smoke Shelf: The smoke shelf is literally a shelf located directly behind the damper. It is the bottom of the chimney as it extends upward from the outside wall.
- Smoke Chamber: The smoke chamber is located just behind the lintel. It is the space in the system where smoke gathers and then rises into the flue.
- Flue: The flue is the liner of the chimney. It is the tube that guides the smoke from your fireplace out into the open.
- Mortar Crown: The mortar crown is literally a layer of mortar applied to the very top of the chimney to shed water and protect your masonry units from the effects of freezing water.
Getting It Right
When we build a chimney in Wellesley, we take every precaution to ensure that your finished structure will be sturdy and reliable. This requires taking some consideration for more than just the chimney itself. For instance, to prevent settling issues, such as cracking and collapse, it is important that the downspouts of your gutter system be directed away from the foundation. Additionally, it is also important that the ground surrounding the base of the chimney be gently sloped to ensure that water will run away from the structure and not seep beneath it.
We also recommend investing in a chimney cap to prevent rainwater and melting snow from dripping down into the flue and gathering on the smoke shelf. When water mixes with soot, it creates an acidic slurry that can seep down into the fire back – or the back wall of the firebox – and destroy mortar joints, which can lead to uncontrolled fires.
In addition to building chimneys, our team of masonry experts can also help you repair any portion of your fireplace system that has fallen into disrepair. It is only natural, over time, that smoke and the repeated cycles of heating and cooling will begin to take their tolls on your cozy hearth. If you have noticed any cracked, loosened or fallen masonry units from the chimney on the rooftop, please call us immediately for a free inspection and estimate. Falling bricks and stones can cause unpredictable damages to both human beings and property. Our masonry company can build a chimney in Wellesley that will last you and your family a lifetime.