New Buck Corporation 18 Manual page 18

ALTERNATE FLOOR PROTECTORS MATERIAL
Floor protector must be 3/8" minimum thickness non-combustible material or equivalent.
With the floor protector or hearth extension material specified as one layer of 2" thick brick
with a K* factor of 5.0, you may use alternate materials as long as the K factor(s) is calculated
as follows:
FORMULA: Required thickness = (K of alternate material/K of millboard) x (thickness
of millboard)
EXAMPLE: An alternate inorganic non-combustible millboard with a K of .9375
would require a thickness as follows:
Required thickness = (.9375/5.0) x 2 in.
K FACTORS OF ALTERNATE MATERIALS
Material
Ceroform 126
Limestone
Concrete
Sandstone
Marble
A hearth extension or floor protector thickness above 4" is generally not acceptable due to cost,
floor load capacity, and look. The alternate we recommend is using Ceroform No. 126
millboard 1/8" minimum and putting any type decorative brick or stone (any thickness) on top
of it.
*The "K" factor represents the thermal conductivity of a material and is the time rate of heat
flow through a homogeneous material under steady-state conditions, through unit area, per unit
temperature gradient in the direction perpendicular to a surface.
= 3/8 inch
K
.21
8.0
8.0
13.0
18.0
16
Required Thickness
1/8"
3.2"
3.2"
5.2"
7.2"