How to Make Plans for a Wood Fireplace

Know your municipality's building codes before starting your plans. Codes affect the size and placement of every aspect of a fireplace; one constructed without regard to the codes is unsafe -- and it will not pass inspection. Two examples of basic fireplace code are that an intake air supply must be provided for the firebox, and that the top of the chimney must be at least 3 feet higher than the highest point of the roof.

Decide the size of the fires you will want, which will determines the width of the fireplace opening. A large, roaring fire can accommodate a large crowd around it, but it quickly consumes a lot of wood. The fireplace should always fit the room size.

Work out the other dimensions of the fireplace starting from the opening width, according to what the building codes demand. For example, according to building code in Allegany County, Maryland, when a fireplace opening is 6 square feet or larger, the hearth extension shall extend at least 20 inches in front of and 12 inches beyond each side of the firebox. In accordance with most standard codes, Buckley Rumford Fireplaces builds it fireplaces so that the inside height of the smoke chamber from the fireplace throat to the beginning of the flue shall not be greater than the inside width of the fireplace opening.

Plan to have a flue that's large enough to handle the start-up of a fire. Too small of a flue means there will not be enough ventilation to carry the initial smoke up the chimney. The minimum flue size you’ll likely have is 7½ inches by 11½ inches, and the maximum is 13 inches by 17½ inches. As with most fireplace measurements, the flue size is determined by the fireplace opening.

Decide how high up the wall the fireplace opening will go. Some hearths are placed at the ground level, while others can be waist high. Heat rises, so the lower the fireplace the longer the heat will have to warm the entire room, but the extra height of the firebox may make maintaining the fire easier on you and make cleanup less messy.

Decide on the hearth, mantel and side materials for your fireplace. Your choices for the hearth and sides are limited to material that is considered fire-resistant by code, such as concrete, brick and stone. The mantel material is more flexible and is oftentimes wood.