30
Heatilator • Birmingham 42-B Installation Manual • 4059-715 • Rev P • 09/28/15
* 2 in. (51 mm)
Continuous,
non-combustible sealant
Tile, stone or other
non-combustible material
Floor constructed of wood or
other combustible material
1 in. Micore and 1/2
in. Durock or
equivalent insulation
(see Table)
Fireplace
Protective
Metal Hearth
Strip
Durock
*
*
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.
Figure 7.5 Hearth Extension Construction
Floor
Noncombustible
Framing Material
Noncombustible
Finishing Material
Protective Metal
Hearth Strips
1 in. Micore and
1/2 in. Durock
or equivalent
insulation
20 in. Min.
Hearth Extension
Note: The bottom of the fireplace
opening is 3-3/4 in. (95.3 mm)
above the bottom of the
fireplace. Finished hearth must
NOT extend above this level.
Noncombustible
Framing Material
HX4 or
equivalent
Figure 7.7 Raised Platform Hearth Extension-Framing
Non-combustible
Finishing Materials
Figure 7.8 Raised Platform Hearth Extension-Finishing
Figure 7.6 Raised Platform Hearth Extension Detail
1. Fireplace Installed Flush on the Floor and
Hearth Extension Raised to Bottom of Firebox
Opening
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 7.5.
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.