Fireplace Construction Procedures

Size

• The size of the fireplace should be appropriate for the room which it is intended to heat. For example, a room of 300 square feet is well served by a fireplace opening 30 inches to 36 inches wide. A larger room needs a fireplace with a larger opening, while a smaller room needs a smaller opening. Fireplaces usually have a greater width than height to match the width-to-height ratio of the walls of an average home.

Dimesions

• The fireplace opening should have a depth of 2/3 its height, so a 30-inch high opening should have a depth of 20 inches, according to the book "Wood Frame House Construction" by L. O. Anderson. The width of the back of the fireplace needs to be about 6 to 8 inches less than the width of the front. Constructing the opening this way helps guide smoke to the rear of the opening and up the chimney.

Hearth

• The floor, or inner hearth, of the fireplace, should reach about 16 inches past the opening. Extending the hearth into the room helps guard against sparks hitting a finished floor. A concrete slab should support the extended area of the hearth. The inner hearth, the area where the fire burns, should be constructed from a heat-resistant material. A good choice is firebrick, brick with a low porosity that can withstand the heat of the wood fires in the grate.

Flue Size

• The proper size of the flue, the passageway that leads smoke and fumes to the outside, depends on the square footage of the fireplace opening. For chimneys 15 feet high or greater, the square footage of the flue should be about one-tenth that of the opening. For chimneys less than 15 feet high, the square footage of the flue needs to be about one-eighth of the opening.