Anatomy of a Masonry Chimney and Fireplace

A masonry chimney is generally considered the traditional type of chimney, as opposed to modern ones that are built with metal. If you’ve wondered how it works, read on as Chimney Doctors takes an under-the-hood look at its parts.

The Chimney

It’s easy to think of the chimney as “the part that expels all the smoke,” or “the part that pokes through the roof”. While both statements are true, chimneys are far more complex, and can be considered as a structure that’s distinct from the fireplace.

• Chimney crown. Let us first take a look at the crown, which is the topmost part of the chimney. Its purpose is to protect the top of the chimney from infiltration by rainwater and small animals without blocking smoke and other particulates as they’re vented.
• Chimney flue. The outer brick lining of a masonry chimney is a shell, much like siding is to an exterior wall. Inside, the flue or chimney liner works as the “throat” — it helps protect the bricks from problems like spalling, efflorescence and mortar deterioration. Flue can be made of materials like fired clay or metal.
• Smoke chamber. The smoke chamber is the transition between the firebox and the flue. It works like an upside-down funnel that prevents smoke and gasses from getting into the living areas.
• Damper. The damper is a plate that is closed when the fireplace is not in use and prevents air leaks.

The Fireplace

The fireplace is the lower half that generates heat. The outermost part is covered by a decorative mantle, which typically has a shelf where decorations, particularly for the holidays, are hung. Underneath it are the following parts:

• Smoke shelf. The smoke shelf is attached to the smoke chamber. It is specifically shaped to push smoke upwards and away from the living areas.
• Lintel. The lintel is a heavy piece of iron that is embedded into the brick, just above the center of the fireplace. It is a load-bearing piece that helps maintain the fireplace’s structure.
• Firebox. This is the business end of the fireplace, the part where firewood is burned. While the term “hearth” is often used interchangeably with “firebox,” the former is actually the bottom part of the latter. The front section that prevents sparks and ash from getting into the living areas, is the hearth extension.
• Ash pit. The ash pit is the opening under the firebox where ashes from the firewood fall. The top is a grille metal door called the ash dump. The ashes are removed through a clean-out or ash pit access door that’s typically accessible from the basement or the outside.

Chimney Doctors provides chimney relining and other chimney services to Saratoga Springs, NY and the surrounding communities. Give us a call at (518) 882-5009, or fill out our contact form to schedule a free, no-obligation consultation.