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B36LA8 & B36RA8 Woodburning Fireplaces
FLOOR PROTECTION
All fireplaces installed over a combustible floor must incorporate a noncombustible earth extension. It is
required to protect the floor in front of the fireplace from both radiant heat and sparks.
Hearth extension dimensions should be determined by using the chart below. Use hearth extensions as il-
lustrated in Figures 5, 10 and 11 or use an acceptable thickness of a durable noncombustible material with
an equal or greater insulating value than K - .43 BTU in/ft
-HR-F°, or a thermal resistance that equals or
2
exceeds R = 1.16. These materials should be covered with a decorative noncombustible veneer.
NOTE: Any noncombustible material with a K factor value that is less than .43, or whose R value is more
than 1.16 or 1/2" thick material is acceptable.
HOW TO DETERMINE HEARTH EXTENSION REQUIREMENTS
The following information is provided to determine required thickness for any noncombustible material when
either the K or R values are known. They are expressed as the following: K = BTU-in/ft
2
-HR-F° or R = HR-
F°/BTU. These materials should be covered by a decorative noncombustible material such as tile, brick,
stone or slate. To determine the thickness needed for a material other than those listed in the chart, use the
following formulas to calculate that which will be an acceptable equivalent.
The ability of insulating material to retard the transfer of heat may be expressed as either Thermal Con-
ductance (C), Thermal Conductivity (K) or Thermal Resistance (R). The mathematical relationship of these
values and the formulas for converting one value to another is as follows:
C = K divided by the material thickness
(Example: C = .43 divided by 1/2 (.50) C = .86)
K = C multiplied by the material thickness
(Example: K = .86 multiplied by 1/2 (.50) K = .43)
R = The material thickness divided by K
(Example: R = 1/2 (.50) divided by .43 R = 1.16)
With either type hearth extension minor shifting of the supporting floor or expansion and contraction may
eventually cause a crack to develop between the hearth extension and the face of the fireplace. To help
prevent the crack from developing, the hearth extension materials must be firmly fastened in place. Wall
ties should be screwed to the face of the fireplace and imbedded n the mortar joints of brick, stone or other
noncombustible materials. The metal safety strip packed with the fireplace must be placed beneath the fire-
place and extended under the hearth extension or into a mortar joint of the hearth extension. In the event
a crack does eventually develop, the metal safety strip will serve as a barrier to prevent sparks or embers
from falling from the fireplace onto combustible flooring materials.
*Refer to Figure 5 for an alternate hearth extension using brick only.
WARNING: The space between the hearth extension and fireplace must be sealed with a noncom-
bustible material. When installing the hearth extension, be careful not to block the heat circulating
air inlets (louvers, slots, etc.) Figure 5
Wall Protection
A model WS wall shield or an equivalent must be installed when the closed end of the fireplace is closer
than 24" from a wall perpendicular to the face of the fireplace. Figures 10 and 11. The WS wall shield should
be attached securely to the wall by driving nails or screws through it into the wall studs. The wall shield
should be covered by a decorative noncombustible material such as brick, tile, slate, etc.
The WS wall shield is constructed of 1" of Micore CV230 insulation board, manufactured by U.S. Gypsum
Corporation, covered by a sheet of galvanized metal. An alternate insulating material with a K factor of .43
or lower can be used. Refer to the preceding section for instructions for selecting an alternate insulating
material. WARNING: If not installed, operated and maintained in accordance with the manufacturer's
instructions, this product could expose you to substances in fuel or from fuel combustion which
can cause death or serious illness and which are known to the State of California to cause cancer,
birth defects or other reproductive harm. Also, operation, installation and servicing of this product
could expose you to airborne particles of glass wool fibers known to the State of California to cause
cancer through inhalation.
8
87D0176
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