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B. Hearth Extension, Building and Fin-
ishing
WARNING! Risk of Fire!
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 & 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.
(1029 mm)
Figure 7.3
Heat & Glo • BAY-40, PIER-40 Installation Manual • 4012-071 • Rev D • 10/03/13
High temperatures, sparks,
72 in.
(1829 mm)
16 in.
(406 mm)
40-1/2 in.
HEARTH
EXTENSION
(shaded)
BAY-40
(1626 mm)
Hearth Extension Dimensions
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 extensions are to be installed only as illustrated to prevent
high temperatures from occurring on concealed combustible
materials.
Table 7.1
R
= 1/k x inches of thickness
Table 7.2
Hearth Extension Insulation Alternatives, R Value = 1.03
Material
Hearth & Home HX3, HX4
USG Micore 300™
USG Durock™ Cement Board
Cement Mortar
Common Brick
Ceramic Tile
Armstrong™ Privacy Guard Plus
Marble
62 in.
(1575 mm)
16 in.
(406 mm)
56 in.
(1422 mm)
26 in.
(660 mm)
to front of
HEARTH
fireplace
EXTENSION
opening
(shaded)
64 in.
PIER-40
k per inch
r per inch
thick
thick
0.49
2.06
0.49
2.06
1.92
0.52
5.0
0.20
5.0
0.20
12.50
0.08
0.46
2.18
14.3-20.0
0.07-0.05
12 in. (305 mm)
from opening of
fireplace
8 in.
(203 mm)
64 in.
(1626 mm)
Minimum
thickness
required
1/2 in.
1/2 in.
2 in.
5 1/8 in.
5 1/8 in.
12 1/4 in.
1/2 in.
14 5/8 in. - 20 3/8 in.
29
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