Masonry Fireplace & Chimney Anatomy

©Don Vandervort, HomeTips

Typical Masonry Fireplace Construction

Classic masonry fireplaces are built in place by masons, using brick, stone, and other masonry materials. Building such a fireplace is expensive—typically costing $5,000 or more—and time consuming.

Real masonry fireplaces require a heavy-duty concrete foundation to bear and distribute the significant weight of the fireplace and chimney. For more about how they are built, see How Fireplaces Work. They’re almost always built where a home is under new construction (a new home or major addition). Traditionally, these fireplaces burn wood but, because of the pollutants they create, many masonry fireplaces are now fitted with gas-burning log sets.

It’s important to note that many fireplaces that appear to be masonry are not actually made entirely from brick, stone, or other masonry materials. Instead, they have a facade of masonry materials but their interiors and chimney flues are high-efficiency appliances manufactured from steel, as discussed below. Bottom line is that this is just a much easier, more affordable way to build a fireplace that is far more efficient than its masonry counterpart.

Construction of a Masonry Fireplace

The construction of a typical classic fireplace, from top to bottom, is shown here. The chimney cap keeps objects from falling into the chimney and, with a spark arrester, keeps sparks from escaping.

The chimney flue, made from insulated metal or terracotta, safely carries combustion gases up the chimney.

The smoke dome and wind shelf are designed to work together to funnel smoke and gases out the chimney.

The damper, a door made of cast iron or steel, regulates the draft up the chimney.

The firebox contains the fire and sends smoke upward. It also maximizes heat radiation into the room.

The ash pit is a fireproof storage area for ash. It’s accessed through a cleanout, a small metal door outside.

The foundation supports the weight of the fireplace and chimney, distributing it evenly to the ground.

What is a Chimney Cricket?

Where a masonry chimney penetrates the roof, you’ll find a chimney cricket. You may ask what—or perhaps who—is a Chimney Cricket?”

Although the word “cricket” immediately conjures up visions of a large insect, on a house it refers to a peaked-shaped structure on the roof—a small, false roof behind a projection such as a chimney. The term probably originated with the games of cricket or croquet, which were first played back in the time of Henry VIII. A roof cricket is shaped like the arch—or peaked-shaped wicket—used in both of these games.

Also called a saddle, a cricket is designed to shed water away from the chimney and other roof projections; it’s usually capped with a large piece of sheet-metal flashing. Sometimes a large flashing that collects water where two roof slopes meet is also called a cricket.

 


Fireplaces & Chimneys

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