To support the weight of the fireplace and chimney, provision must be made in the foundation plans. Most plans use a solid reinforcement for concrete footer. This footer is usually 12″ (305mm) thick and extends at least 12″ (305mm) past the perimeter of the chimney.
Fireplaces are designed in three types:
1. Constructed totally on the site.
2. Using a manufactured firebox and flue system.
3. Freestanding units.
Major components of fireplace and chimney structure:
3. smoke chamber
4. flue support
7. steel anchor straps
9. terra cotta flue lining
11. smoke shelf
12. angle-iron brace
14. ash pit
The main part of the fireplace is the firebox. The firebox reflects heat and draws smoke up the chimney. Included in the firebox are the sides, back, smoke chamber, flue, throat and damper. Most of the fireboxes are constructed in a factory. The constructor places the firebox in the proper location in the chimney construction and lines it with firebrick. Materials used in fireplaces and chimneys is usually of brick, stone or concrete. Hearth should be constructed of fire-resistant material such as brick, tile, marble or stone. The best method of drawing the construction details of a fireplace is to prepare a sectional drawing. This will show the position of the firebox and the size of materials used in the footer, hearth, face, flue and cap of the chimney. Showing also the relationship of the chimney to the floor and ceiling lines of the structure.
Extending from the footer through the roof of the house is the chimney. The footer must be of sufficient size to support the entire weight of the chimney. The chimney extends above the roof line. Its height above the roof line varies, local building codes in most areas scale its distance as 2′ (610mm). The chimney is secured to ceiling and floor joists by iron straps embedded in the brick work. The constructor must also indicate the type and size of flues to be inserted in the chimney. One flue is necessary for each fireplace or furnace leading into the chimney. Fireplaces add warmth and atmosphere to a room. However, most of the heat produced by some fireplaces goes up the chimney. To reduce this heat loss and redirect some of this heat, warm-air outlets, balanced by cold-air outlets, can be installed.
Freestanding metal fireplaces constructed of heavy gauge steel are available in a variety of shapes. They are relatively light wood burning stoves and therefore need no concrete foundation for support. A stove pipe leading into the chimney provides the exhaust flue. Prefabricated fireplaces do not require a foundation to support their weight. They are complete, ready-to-install fireplaces. Nevertheless, a fire-resistant material such as concrete brick, stone or tile must be used beneath and around these fireplaces.