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Heat & Glo • Rutherford 42-B Installation Manual • 4059-712 • Rev O • 09/28/15
3. Fireplace Opening and Hearth Extension
Flush with the Floor
Non-combustible flooring a minimum of 20 in. (508 mm)
in front of and 12 in. (305 mm) to each side of the fuel
opening is required.
The hearth framing must be constructed of non-com
-
bustible materials (such as metal framing or equivalent
material) and placed on HX3(s) or HX4(s) and 1/2 in.
Durock, or equivalent material. Refer to Figure 7.10.
When creating the platform, allow for the thickness
of the non-combustible finishing materials
.
Seal gaps between the hearth extension and the front
of the fireplace with a bead of non-combustible sealant
or grout.
Non-combustible Finishing Material
Protective Metal
Hearth Strip
20 in. Min.
Hearth Extension
1 in. Micore and
1/2 in. Durock
or equivalent
insulation
Finished
Floor
Note:
The bottom of the fireplace opening
is 3-3/4 in. (95.3mm) above the bottom of
the fireplace. Finished hearth must NOT
extend above this level.
Bottom of
Fireplace
Opening
Figure 7.10 Flush Hearth Extension Side View
C. Non-Combustible Sealant Material
After completing the framing and applying the facing
materials over the framing, a bead of non-combustible
sealant must be used to close off any gaps at the top
and sides between the fireplace and hearth.
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.
Non-combustible Sealant
Figure 7.11 Place Non-combustible Sealant
