Heatilator • LM42 • Installers Manual • 4087-901 • Rev A • 04/14/16
35
1. If the hearth extension is more than 12 inches below the fireplace opening an insulation barrier is not required but
must be made of tile, stone, or other non-combustible material.
Figure 7.3
More than 12 in. (305mm)
Non-combustible
Hearth
Seal with grout, motar, or
high temperature sealant
Figure 7.4
2. If the hearth extension is flush or less than 12 inches below the fireplace opening, the structure must be made of all
non-combustible material (such as metal framing or equivalent material) and sitting on 1/2 in. Micore or other material
with an R value of 1.03.
When creating the platform, allow for the thickness of the non-combustible finished materials.
Seal gaps between the hearth extension and the front of the fireplace with a bead of non-combustible sealant or grout.
Floor
Noncombustible
Framing Material
Noncombustible
Finishing Material
1/2 in. Micore
or equivalent
insulation
Note: If the hearth extension is
flush or less than 12 in. (305 mm)
below the opening it must be all
non-combustible material.
Flush or less than
12 in. (305 mm)
below fireplace
opening
Seal with grout,
motar, or high
temperature
sealant
Protective metal
hearth strips