Fireplace size should be in proportion to the room size. Extra large fireplaces do necessarily produce more heat than smaller structures. A fireplace 30 to 36 inches wide is generally suitable for a room with 300 square feet of floor. Overall fireplace dimensions for 15 typical fireplaces are shown in our Table of Fireplace Dimensions.
While any type of brick may be used for the outside of the fireplace, the fire pit must be lined with a high-temperature fire clay or firebrick. The pit is nearly always sloped forward from a point 14 inches above the hearth to the level of the damper, usually five to eight inches above the breast wall of the fireplace, and sloped on both sides. This construction deflects both flame and heat forward. Products of combustion pass off through the damper, while maximum heat is deflected into the room.
It is important that the slope of the smoke chamber is identical on both sides. It is helpful to use a form made of two boards with connecting braces during construction. This form helps give the bricks a proper slope and assists in providing a smooth surface. Both of these are crucial for the correct discharge of smoke. The sloped back brings the damper forward of the flue, to a position slightly back from the breast wall of the fireplace. This leaves room for an ample smoke shelf behind the damper. The smoke shelf acts as a barrier for the down draft and sends it back up the stack the damper has a rear position no smoke shelf is possible. In this case soot falling down the chimney comes through the damper opening and often into the room. Also, the rear position sacrifices much heat.
Every fireplace should include a brick or stone hearth where hot wood embers may fall safely. Hearths are generally built out at least 16 inches from the fireplace. Many hearths are raised several inches above the floor level. This raises the fireplace itself and makes it easier to tend the fire.
Many fireplaces have ash pits or ash dumps. These are cavities in the floor or wall of the fireplace where the ashes are stored. Floor pits should be equipped with a heavy metal grate, which prevents large pieces of wood from dropping in the pit. The cavity can be lined with a metal box that is taken out for cleaning or it can be accessed from a second door in the basement or outside the home.
Bon Tool Co. has made a serious effort to provide exact and current information, but does not guarantee the accuracy of the data. Bon Tool Co. cannot assume responsibility for the application of information nor guarantee results.
