17
ODSHR Outdoor Woodburning Fireplace
20002264
COMMON MATERIALS AND FACTORS
MATERIAL
K*
R
MINIMUM
THICKNESS
EH2416
Common Brick
0.458
5.0
1.09
0.50 in.**
0.10 5.46 in.**
(CFM Corporation)
R Value is for
���
inch.
* Units of K = BTU/SQ FT/HR/˚F/IN
** Thickness of Listed Material
FP533ADD
Addendum
6/1/99 djt
8/4/99 changed .2 to .1
one inch to 1/2 inch djt
FP533ADD
Fig. 28
Hearth extension material factors.
FP1169
Type A floor
12/20/01 djt
Seal Cracks Between
Fireplace and Hearth
Extension with Non-
combustible Material
Noncombustible
Decorative Covering
May be Installed
or
.018" Minimum
Sheet Metal
Fireplace
Hearth
Lower Sur-
round
Safety Strips
Must be Over-
lapped 1/2" Min.
Minimum Insula-
tion Value R-3.28
(Refer Table 4)
Min. Thickness
(Refer to Table 4)
2
¹⁄₂
" Min.
Combustible
Floor
FP1169
FP1170
Type B floor
12/20/01 djt
Safety Strips
Must be Over-
lapped 1/2" Min.
Minimum Insulation
Value R-0.94
1/4" Min.
Thickness
Combustible
Floor
8" Max.
Thickness
Seal Cracks Between Fireplace
and Hearth Extension with Non-
combustible Material
Cement
Blocks
Lower Sur-
round
Fireplace
Hearth
FP1170
Fig. 29
Protection of adjacent combustible side walls and
hearth extension dimensions.
FP1171
sealing detail
12/20/01 djt
Wall Covering
2 x 4 Header
- Do Not Notch
at Ledge
Brackets
Fig. 20
Hearth Extension
Hearth
Extension Insulation
Molding used to
Fasten Hearth
Extension
in Place
Majestic Safety Strips Must
be Overlapped 1/2" Min.
Seal Crack Between
Fireplace and Hearth
Extension with
Noncombustible Material
FP1171
Fig. 30
Sealing detail.
Alternate noncombustible materials may be used pro-
viding the (total) thermal resistance (Rt value) of the al-
ternate material employed is greater than or equal to R
= 1.09. Thermal resistance (R) or thermal conductivity
(K), may be obtained from manufacturer of the material.
Factors are related by the formula K = 1/R. (Fig. 28)
T = given thickness
R = thermal resistance for a given thickness (T)
K = thermal conductivity
Noncombustible material with a lower R value may
be used, provided thickness of material is sufficiently
greater to maintain an equivalent (total) thermal resis-
tance (Rt).
Example of Determining Hearth Extension
Equivalents
To determine the thickness required for any
new
mate-
rial:
NEW
K of new material (per inch)
thickness
required +
X
of listed
thickness
K of listed material (per inch)
material
Example for Common Brick
T (new) = 5.0/0.458 x 0.50 in. =
5.46 in.
(new required
thickness).
