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8 in. (203mm) minimum
from each side of
fuel opening
A
B
Figure 7.6 Minimum Hearth Extension Dimensions
Model # PIONEER III
A
B
in.
42
20
mm
1067
508
• Fireplace and Hearth Extension flush on the floor
Non-combustible flooring a minimum of 20 in. (508 mm)
in front of and 8 in. (203 mm) to either side of the fuel
opening is required as shown in Figure 7.6.
The construction of, and materials used for a hearth
extension are shown in Figure 7.7. A hearth extension
of this construction may be covered with any non-
combustible decorative material and may have a
minimum thickness as per Figure 7.6. Seal gaps between
the hearth extension and the front of the fireplace with a
bead of non-combustible sealant or grout.
Fascia
Outer Can
Flange
Protective metal
hearth strip
Tile,marble or other
non-combustible finish material
Minimum 2 in. (51mm) Cement Board or
equivalent, (or one piece HX4)
Minimum 20 in. (508mm) in front and
8 in. (203mm) on sides to fuel opening
Combustible Floor
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. . . . . . . . . . .
Non-combustible
material supplied
with unit.
. . . . . . . . . . .
Non-combustible sealant or grout
Tile,marble or other
non-combustible
finish material
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Figure 7.7 Fireplace and Hearth Extension Flush on the Floor.
D. Finishing the Hearth Extension
Table 7.1
R
= 1/k x inches of thickness
Table 7.2
WARNING! Risk of Fire!
High temperatures, sparks, em-
bers or other burning material falling from the fireplace
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 fireplaces 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 7.5 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!
You must comply with all minimum air space clearances
to combustibles as specified. Framing or finishing material
used on the front of, or in front of, the fireplace closer than
the minimums listed must be constructed entirely of non-
combustible materials (i.e., steel studs, concrete board,
etc.). Failure to comply may cause fire.
• Fireplace installed flush on the floor and hearth extension
raised to bottom of fascia:
Non-combustible flooring a minimum of 20 in. (508 mm)
in front of and 8 in. (203 mm) to either side of the fuel
opening is required (see Figure 7.5).
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 in.
Marble
14.3-20.0
0.07-0.05
14 5/8 in. - 20 3/8 in.
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Quadra-Fire • PIONEER - III • 4182-901 Installation Manual • Rev C • 07/19