Masonry Magazine February 1983 Page. 26
NOMINAL 1 IN. (25 mm)
AIR SPACE
MINIMUM
12 IN. (300 mm)
NOMINAL 1 IN. (25 mm)
AIR SPACE
FIRE CLAY FLUE LINER
A
REAR CLEAN-OUT DOOR
FOR BAFFLE CHAMBER
FRONT CLEAN-OUT DOOR
FOR BAFFLE CHAMBER
REFRACTORY CONCRETE SLAB
FIRE BRICK
EXTERIOR WYTHE
OF MASONRY
SHOWN WITH
METAL TIES
AND JOINT
REINFORCEMENT
EXTENDED HEARTH.
MINIMUM 20 IN.
(500 mm)
FIREBOX DOOR
FIREBOX
NOMINAL 1 IN. (25 mm)
AIR SPACE
CLEAN-OUT
ASHPIT
SOLIDLY FILLED
COLLAR JOINT
REINFORCED
CONCRETE SLAB
AAALAMATATA
(SIDE SECTION)
Brick Masonry Heater with Horizontal Baffles
FIG. 3
The chimney should be at least 64 sq in. (40 000 mm²). The chimney should be constructed with clay flue liners with two wythes of brick surrounding the flue liners in such a way as to maintain a nominal 1-in. (25 mm) air space between the flue liners and the interior wythe of brick.
Clearances between the brick masonry heater exterior walls and any combustible materials should be at least 12 in. (300 mm). This will require the masonry heater to be either centrally located within a room, or located adjacent to a brick masonry or other non-combustible interior wall with at least a 1-hr fire rating. To ensure clearances, it may be beneficial to provide an extended hearth around the entire masonry heater. Construction using the proper clearances also maximizes the use of the warmed brick masonry surface as radiant heat sources.
Base Assembly
The base assembly includes the foundation, extended hearth, and ash drop. These features are the same for both the vertically and horizontally baffled Russian-style heaters.
Foundation
The foundation must be adequate to support the mass of the brick masonry heater and the masonry chimney. When designing the foundation, care should be taken to account for soil types and foundation conditions. Undisturbed or well-compacted soil will generally be sufficient, however, some types of soil or foundation conditions may require additional analysis, which may result in the need for special soil treatment or a unique foundation design.
Building codes generally require that the foundation be at least 12 in. (300 mm) thick, and in plan view, extend a minimum of 6 in. (150 mm) beyond each face of the masonry heater. The foundation should be positioned so that the bottom of the footing is below the frost line to reduce the possibility of "heaving."
Unless the foundation is a thickened slab in a newly constructed slab-on-grade structure, masonry is usually used to construct the base assembly to the height of the hearth support. The hearth support may be solid masonry construction carried up from the foundation to support the entire hearth area. To conserve materials, the masonry is usually brought up only equal to the dimensions of the masonry heater itself and the brick masonry of the base assembly is corbeled out to form the support for the extended hearth. See Figures 1 through 4. An individual corbel should not exceed one-half the unit height nor one-third of the unit thickness. The total projections of the corbel should not exceed one-half the thickness of the base assembly, nor one-half of the thickness of the solid masonry wall forming the base assembly. A further