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Majestic Biltmore Series • SB100 • 4013-303 Installers Manual • Rev H • 08/20
B. Hearth Extension, Building and Fin-
ishing
Table 7.1
R
= 1/k x inches of thickness
Table 7.2
WARNING! Risk of Fire!
High temperatures, sparks,
embers or other burning material falling from the fire
-
place may ignite flooring or concealed combustible
surfaces.
• Protective metal hearth strips MUST be installed.
• Hearth extensions MUST be installed exactly as
specified.
A hearth extension must be installed with all fire
-
places to protect the combustible floor in front of the
fireplace from both radiant heat and sparks.
• You MUST use a hearth extension with this
fireplace.
• Refer to Figure 7.3 for minimum dimensions.
• This fireplace has been tested and approved for use
with a hearth extension insulated to a minimum R
value of 1.03.
• The hearth extension material MUST be covered
with tile, stone or other non-combustible material.
• Manufactured hearth materials will usually have a
published
R value
(resistance to heat) or
k value
(conductivity of heat). Refer to the formula in Table
7.1 to convert a k value to an R value,
• Refer to Table 7.2 for hearth extension insulation
alternatives.
WARNING! Risk of Fire!
Hearth extensions are to be installed only as illustrated to prevent
high tempertures from occurring on concealed combustible
materials.
WARNING! Risk of Fire!
• Maintain clearances.
• Use only non-combustible material below standoffs, material
such as cement board is acceptable.
• Framing or finishing material used on the front of the fireplace
closer than the minimums listed, must be constructed entirely
of non-combustible materials (i.e., steel studs, concrete board,
etc.).
WARNING!
Risk of Fire!
Hearth & Home Technologies is not responsible for
discoloration, cracking or other material failures of
finishing materials due to heat exposure or smoke.
• Choose finishing materials carefully.
Figure 7.3 Hearth Extension Dimensions
74 in.
(1880 mm)
50 in.
(1270 mm)
12 in.
(305 mm)
12 in.
(305 mm)
20 in. (508 mm)
minimum
Hearth Extension Insulation Alternatives, R Value = 1.03
Material
k per inch
thick
r per inch
thick
Minimum
thickness
required
Hearth & Home HX3, HX4
0.49
2.06
1/2 in.
USG Micore 300™
0.49
2.06
1/2 in.
USG Durock™ Cement Board
1.92
0.52
2 in.
Cement Mortar
5.0
0.20
5 1/8 in.
Common Brick
5.0
0.20
5 1/8 in.
Ceramic Tile
12.50
0.08
12 1/4 in.
Armstrong™ Privacy Guard Plus
0.46
2.18
1/2 in.
Marble
14.3-20.0
0.07-0.05
14 5/8 in. - 20 3/8 in.
