Traditional Fireplace Construction

Fireplace Basics

• All conventional masonry fireplaces are comprised of inner and outer shells. The inner shell where the fire is built is made from fireproof materials to contain the fire and control heat and smoke. The outer shell supports the internal structure, contains the accessories needed for the fireplace to properly function and provides a frame for the fireplace.

Inner Shell Components

• The foundation of the fireplace supports the rest of the structure. It has to be strong enough to hold heavy logs and have dimensions large enough to accommodate piles of kindling and firewood. An ash pit beneath the foundation collects cold ashes to keep the interior clean and functioning. The inner hearth, or firebox, is where you build the fire, either directly on the surface or on top of a grate to let air flow on all sides of the fire. The outer hearth extends from the front of the fireplace to catch errant embers and support a fireplace screen to prevent ash from entering the room. Fireplace butt walls support the wall behind the firebox.

Outer Shell Elements

• To operate efficiently and keep the room free of smoke, you need outer shell elements. A smoke shelf protrudes from the back of the firebox to counter downdrafts and send them back up the flue. A damper is a metal door installed at the base of the opening between the fireplace and the chimney. It opens and closes with a pull handle or spring to regulate air flow in and out of the fireplace. The smoke chamber is the area below the flue that gathers and dispenses smoke and gases before they enter the room. Right above the smoke chamber is the flue, which extends upward from the top of the smoke chamber and directs the smoke into the chimney.

Chimney System

• The chimney is typically made of brick, concrete or other fireproof materials. It surrounds the flue as it reaches the roof and directs the smoke into the atmosphere. Chimneys have caps that prevent rain and snow from falling into the fireplace and keep birds and animals from nesting in the chamber. Pieces of mesh wire attached to chimney tops keeps sparks and hot debris from escaping and creating fire hazards. Some chimneys have rotating hoods, or chimney cowls, which swirl to prevent excessive downdrafts in the fireplace.