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115386-01E 5
HEARTH EXTENSION
A hearth extension projecting a minimum of
20" in front of and a minimum of 12" beyond
each side of replace opening is required to
protect combustible oor construction in front
of replace. Fabricate a hearth extension
using a material which meets the following
specications: a layer of noncombustible,
inorganic material having a thermal conductiv-
ity of K=0.84 BTU IN/FT, HR. F (or less) at 1"
thick. For example, if material selected has
a K factor of 0.25, such as glass ber, the
following formula would apply:
0.25 x 1.0" = 0.30" thickness required
0.84
Thermal conductivity "K" of materials can be
obtained from manufacturer or supplier of
noncombustible material. If hearth extension
is to be covered, use noncombustible mate-
rial such as tile, slate, brick, concrete, metal,
glass, marble, stone, etc. Provide a means
to prevent hearth extension from shifting and
seal gap between replace frame and hearth
extension with a noncombustible material
(see Figure 3).
WARNING: Hearth extension
is to be installed only as shown
in Figure 3.
FIREPLACE INSTALLATION
Continued
Figure 3 - Hearth Extension
Seal Gap
Fireplace Front
Ember Protector
Fireplace Front
Elevated
Do Not Block Louver
Ember Protector
Seal Gap
Hearth
Extension
NO
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