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126601-01_J
8
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 6).
WARNING: Hearth extension is to be installed only
as shown in Figure 6.
Figure 6 - 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 7). Woodwork such as
wood trims, mantels or any other combustible material projecting from
front face must not be placed within 12" (36" Models) or 18" (42/50"
Models) of fireplace opening. Combustible materials above 12" (36"
Models) or 18" (42/50" Models) and projecting more than 1
1
/
2
" from
fireplace must not be placed less than 15" (36" Models) or 21" (42/50"
Models) 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 7.
Figure 7 - Mantel Clearances to Combustible Material
12
1
/
4
"
(312 mm)Ref.
6" (153 mm)
Ref.
15" (381 mm) Min.
(36" Models)
21" (534 mm) Min.
(42/50" Models)
12" (305 mm) Min.
(36" Models)
18" (458 mm) Min.
(42/50" Models)
1
1
/
2
" (39 mm)
Max.
3" (77 mm)
Nom.
33°
Combustible
Material
Safe Zone for
Projection of
Combustible
Materials
Fireplace Opening
Upper Section
of Fireplace
FIREBOX
SAFE ZONE
Top View of Fireplace
4
1
/
2
" (115 mm)
7
3
/
4
" (197 mm)
36" Models
11
1
/
2
" (293 mm)
(42/50" Models)
Min. to
Perpendicular
Side Wall
12" (305 mm)
36" Models
18" (458 mm)
42/50" Models
33°
Combustible
Material Must
Not Overlap
Front Face
3" (77 mm) Max.
