52 7/8"
27"
53 1/8"
68"
20"
FLOOR
COMBUSTIBLE
26 3/8"
WARNING: THE HEARTH EXTENSION AND THE
METAL SAFETY STRIP SHOULD BE INSTALLED
ONLY IN A HORIZONTAL RELATIONSHIP TO THE
FIREPLACE, AS ILLUSTRATED.
METAL SAFETY STRIP
HEARTH PROTECTOR
METAL
SAFETY STRIP
HEARTH EXTENSIONS
FLOOR LINE WITH RAISED HEARTH
TOP OF
RAISED HEARTH
12" (MIN)
20"
(MIN)
12" (MIN)
F
loor
p
rotectIon
The ability of insulating material to retard the transfer of heat may be expressed as either Thermal Conductance
(C), Thermal Conductivity (K), or Thermal Resistance (R). The mathematical relationship of these values and
the formulas for converting one value to another is as follows:
C=K divided by the material thickness
(Example C = .43 divided by 1/2 (.50)
C = .86)
K = C multiplies by the material thickness
(Example K = .86 multiplied by 1/2 (.50)
K = .43)
R= The material thickness divided by K
(Example R = 1/2 (.50) divided by .43
R = 1.16)
With either type hearth extension minor shifting of the supporting floor or expansion and contraction may even-
tually cause a crack to develop between the hearth extension and the face of the fireplace. To help prevent
the crack from developing, the hearth extension materials must be firmly fastened in place. Wall ties should
be screwed to the face of the fireplace and imbedded in the mortar joints of brick, stone, or other non-com-
bustible materials. The metal safety strip packed with the fireplace must be placed beneath the fireplace and
extended under the hearth extension or into a mortar joint of the hearth extension as shown by Figures 9, 13,
and 14. In the event a crack does eventually develop, the metal safety strip will serve as a barrier to prevent
sparks or embers from falling from the fireplace onto combustible flooring materials.
10
F
Igure
12
F
Igure
11
53D9026
