FirePlaceConstruction.com | Building a Fireplace | Fireplace Components | Fireplace Layout

Parts of a Fireplace

A fireplace must be constructed to be strong, stable, and fireproof. Each part of the fireplace must be designed and constructed to perform its specified functions if the fireplace is to work efficiently and to last for many years.

On this site the major parts of a fireplace are described and explained so that the bricklayer can accurately read plans and specifications- the instructions that tell how a particular fireplace should be constructed.

Each particular fireplace may have fewer or more individual parts than the ones described in these illustrations and explanations, or some of the parts may be combined into one unit. However, an understanding of the parts included in the illustration will enable the bricklayer to read plans for different types of fireplaces.
Click a number on this cross section
of a masonry fireplace to view its description.

This sectional view shows how a fireplace is composed of an inner and an outer shell which are bonded together with mortar or grout. The inner shell, which surrounds the fire and draft, includes the firebox, smoke chamber, and flue lining. Fireproof materials are used to form the inner shell of the fireplace since control of fire, heat, and smoke are the principal functions of the inner shell.

The outer shell, made from building brick or standard masonry units, supports and surrounds the inner shell. The foundation, ash pit, outer hearth, and chimney walls are parts of the outer shell, which provides structural support and stability.

1. Foundation

A fireplace is supported by and built on its own foundation; in some building codes, the foundation is called a footing. Lay up the fireplace foundation so that it is separate from the building's foundation and has the proper dimensions and reinforcement.

2. Ash Pit

Ashes from the fire can be swept into the ash pit and removed at a later time. The ashes are swept into the ash pit through an ash dump in the inner hearth and removed through a cleanout door. Construct the ash pit so that the ashes can be deposited and removed. Make sure that it is strongly resistant to moisture penetration. If the old ashes get wet they can cause an offensive odor.

3. Inner and Outer Hearth

The inner hearth is the surface directly under the fire. It forms the floor of the firebox. The outer hearth is placed directly in front of the fireplace opening on top of the floor in the room. therefore protecting the floor from sparks that may fall or fly out of the firebox. The inner and outer hearth work together as a fire protecting surface; there must not be any cracks or voids in the hearths because this defeats their fireproofing purpose.

4. Fireplace Butt Walls

The butt walls support and enclose the firebox. These walls extend from the foundation to the bottom of the flue where the chimney starts. Standard masonry units are used to lay up the butt walls, and the same units are used to lay up the chimney.

5. Firebox

The openings and surfaces directly adjacent to the fire form the firebox. The fireplace opening and the flue opening must be accurately dimensioned for effiicent heating and smoke removal. The side and back walls of the firebox must be properly dimensioned and sloped to reflect heat into the room. Firebrick, tightly joined (1/8"), are used to lay up most fire boxes.

6. Smoke Shelf

Downdrafts, which are currents of air that move down the chimney, are reflected back up the flue by the smoke shelf. The smoke shelf projects out from the rear butt walls and has a curving upper surface.

7. Damper

This is a mechanical device which opens and closes to regulate the draft. The damper must be installed so that it can be opened and closed freely and so that heat and smoke will not escape around its sides.

8. Lintel

The lintel is an angle iron which must be placed across the span of the fireplace opening. It supports the masonry units that will be laid over the opening. Install the lintel with the proper bearing and insulation to prevent failure due to imposed loads or heat expansion.

9. Smoke Chamber

The smoke chamber extends from the throat to the bottom of the flue. It collects and discharges smoke and combustion gases and reflects downdrafts.

10. Flue

The flue is a vertical opening through the chimney which extends from the smoke chamber to the top of the chimney. The principal functions of the flue are to create the draft and discharge smoke. The specified size of the flue opening must be maintained for the height of the flue, and all joints within the flue must be filled solid to prevent leaks.

11. Chimney

The chimneyconsists of the masonry units laid around the flue, the flue liner, and other objects such as anchors, reinforcement, and flashing. The chimney walls and the sections of the flue liners are laid up as part of one operation when constructing the chimney.

12. Chimney Top

The top of the chimney must be at a specified height above the roof, and it must be constructed to include the objects specified such as: a chimney cap for moisture protection, a spark arrester for fire protection, and a hood to reduce downdrafts.