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NOTE: DIAGRAMS & ILLUSTRATIONS NOT TO SCALE.
18
Figure 47
FINISH TO YOUR TASTE
There are a wide variety of “finished looks” for
these fireplaces, from formal wall decor with
elaborate mantels to rustic wood paneling or
warm brick facings.
Only noncombustible materials like stone, tile,
brick, etc., may overlap the black front facing.
Do not extend these materials beyond the black
facing and into the firebox area. Be sure not to
interfere with the installation and operation of
glass doors or block the upper or lower grilles.
Seal all joints between the black facing and wall
surrounds to prevent air intrusion. Use non-
combustible caulking material only to seal the
black metal facing to the surround material on
the finished wall.
7-3/4"
(197mm)
Max. Thickness of Hearth Extension when
LBR Models are on the Floor
Figure 48
1-1/2"
(38mm)
Max. Thickness of Hearth Extension when
LBC Models are on the Floor
WARNING: THE CRACK BETWEEN THE
FIREPLACE AND THE HEARTH EXTEN-
SION MUST BE SEALED WITH A NON-
COMBUSTIBLE MATERIAL.
WARNING: WHEN INSTALLING HEARTH
EXTENSION IN FRONT, THE FIREPLACE
MUST BE RAISED IF HEIGHT OF HEARTH
EXTENSION EXCEEDS 7-3/4" (197MM)
(LBR MODELS) ABOVE THE BOTTOM OF
FIREPLACE (
FIGURE 47
).
WARNING: THE FIREPLACE MUST BE
RAISED IF THE HEIGHT OF THE HEARTH
EXTENSION EXCEEDS 1-1/2" (38 MM)
(LBC MODELS) ABOVE THE BOTTOM OF
THE FIREPLACE (
FIGURE 48
).
Secure the hearth extension to the floor to
prevent possible shifting.
Figure 46
Side Wall cannot
be Closer than 12"
(305mm) under
any Circumstances
A
B
C
C
D
Wall
Shield
Note: Any noncombustible material whose k
value is less than .84 or whose r value is more
than 1.19 is acceptable.
If the fireplace is installed on a combustible
floor, use the metal safety strips (provided)
on the floor extending half under the fire-
place and half under the hearth extension
(refer to
Figures 6 & 7)
.
A wall shield is required where a continuous
perpendicular side wall is within 12" of the
fireplace opening (
Figure 46 )
. Use a 36" W x
36" H wall shield constructed of a durable,
noncombustible material having an equal or
better (lower k value) insulating value than k =
.54 BTU IN/FT
2
HR °F. At no time may a
perpendicular side wall be located closer than
9" from the fireplace opening.
If fireplace is installed diagonally across a 90°
corner; no wall shields are required.
Calculating Minimum Thickness if Multiple
Materials are Used
At times it is important to know what
combination of materials are acceptable for
use as floor protection. The “R values” are
used to determine acceptable combinations of
materials because “R values” are additive where
r and k values are not.
“R value” = 1/k = “r” x thickness of material
used
Example:
Given that the required “R value”
for a suitable floor protector used must be
equal to or greater than:
“R” = r
L
x T
L
= 1.19 x 1” = 1.19.”
If it is desired to elevate a marble hearth ex-
tension to a level of 5” or more above the floor
surface. What combination of noncombus-
tible materials can be used to accomplish this?
If common brick is used so that the 3 1/2”
dimension is the height, “R” for the common
brick becomes:
brick
“R”
M
= r
M
x T
S
= 0.20 x 3 1/2" = .70
Using 1/2” of mortar to set the brick, “R” for
the mortar is calculated as follows:
mortar
“R”
M
= r
M
x T
S
= 0.20 x 1/2" = .10
Next, a 3/4" marble slab set in 1/2" mortar cov-
ers the brick, “R” for the marble and mortar
becomes:
marble
“R”
M
= r
M
x T
S
= 0.05 x 3/4" = .038
mortar
“R”
M
= r
M
x T
S
= 0.20 x 1/2" = .10
The sum of all “R values” is: .70 + .10 +. 038
+ .10 = .938
This would NOT be an acceptable combination
of material for the hearth extension since the
total calculated “R value” of the materials used
is under the required “R value” of 1.19. An
additional layer of insulating materials must
be used.
Note:
Also see NFI Certification Manuals for
expanded explanation on calculating “R val-
ues” when multiple materials are used.