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126640-01D
7
FIREPLACE INSTALLATION
Continued
HEARTH EXTENSION
A hearth extension projecting a minimum of 20" in front of and a
minimum of 12" beyond each side of fireplace opening is required
to protect combustible floor construction in front of fireplace. Fabri-
cate a hearth extension using a material which meets the following
specifications: a layer of noncombustible, inorganic material having a
thermal conductivity of k=0.84 BTU IN/FT, HR. F (or less) at 1" thick.
For example, if the material selected has a k factor of 0.25, such as
glass fiber, 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 manufac-
turer or supplier of noncombustible material. If hearth extension is
to be covered, use noncombustible material such as tile, slate, brick,
concrete, metal, glass, marble, stone, etc. Provide a means to prevent
hearth extension from shifting and seal gap between fireplace frame
and hearth extension with a noncombustible material (see Figure 5).
WARNING: Hearth extension is to be installed only
as shown in Figure 5.
Figure 5 - Hearth Extension
Seal Gap
Fireplace Front
Ember Protector
Fireplace Front
Raised Hearth
Fireplace Front
Elevated
Ember Protector
Ember Protector
Seal Gap
Hearth
Extension
MANTELS
A mantel may be installed if desired (see Figure 6). Woodwork such
as wood trims, mantels or any other combustible material projecting
from front face must not be placed within 18" of fireplace opening.
Combustible materials above 18" and projecting more than 1
1
/
2
" from
fireplace must not be placed less than 21" from the top opening of the
fireplace (NFPA 211, Section - Clearance from Combustible Material).
Mantels or any other combustible material also may come up to side
edge of black metal face of fireplace as long as projections from front
face fall within limit shown in Figure 6.
Figure 6 - Mantel Clearances to Combustible Material
12
1
/
4
" Ref.
6"
Ref.
21" Min.
18" Min.
1
1
/
2
" Max.
3" Nom.
33°
Combustible
Material
Safe
Zone for
Projection of
Combustible
Materials
Fireplace Opening
Upper
Section of
Fireplace
FIREBOX
SAFE ZONE
Top View of Fireplace
3" Max.
4.5"
18" Min. to
Perpendicular
Side Wall
11.5"
33°
Combustible
Material Must
Not Overlap
Front Face