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109036-01J 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).
is to be installed only as shown
FIREPLACE INSTALLATION
Continued
Figure 3 - Hearth Extension
Seal Gap
Fireplace Front
Ember Protector
Fireplace Front
Raised Hearth
Fireplace Front
Elevated
Ember Protector
Ember Protector
Seal Gap
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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