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125655-01B
6
Note: For outdoor installations, fireplace
enclosure must allow for adequate drainage
and fresh air ventilation. It is recommended
that a sealed, corrosion resistant catch pan
with provision for drainage be installed under
fireplace within fireplace enclosure.
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. Fabricate a hearth extension
using a material which meets the following
specifications: a layer of noncombustible,
inorganic material having a thermal conduc-
tivity 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 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 fireplace frame and hearth
extension with a noncombustible material
(see Figure 5).
WARNING: Hearth extension
is to be installed only as shown
in Figure 4.
FIREPLACE INSTALLATION
Continued
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 STD
211, Sec. 7-3.3.3).
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
