Hearth Extension; Combustible Material - Desa ICBO# 3507 Owner's Operation And Installation Manual

Fireplace inSTallaTion
Continued

HEARTH ExTENSION

A hearth extension projecting a minimum of 20"
in front of and a minimum of 12" beyond each
side of the fireplace opening is required to protect
combustible floor construction in front of the fire-
place. Fabricate a hearth extension using a material
which meets the following specifications: a layer
of noncombustible, inorganic material having a
thermal conductivity of K=0.84 BTU IN/FT, HR.
F (or less) at 1" thick. For example, if the material
selected has a K factor of 0.25, such as glass fiber,
the following formula would apply:
0.25 x 1.0" = 0.30" thickness required
0.84
Thermal conductivity "K" of materials can be
obtained from the manufacturer or supplier of the
noncombustible material. If the hearth extension
is to be covered, use noncombustible material such
as tile, slate, brick, concrete, metal, glass, marble,
stone, etc. Provide a means to prevent the hearth
extension from shifting and seal gap between the
fireplace frame and hearth extension with a non-
combustible material (see Figure 3).
WARNING: Hearth extension
is to be installed only as shown
in Figure 3.
Fireplace Front
Ember Protector
Fireplace Front
Raised Hearth
Ember Protector
Fireplace Front
Elevated
Ember Protector
Figure 3 - Hearth Extension
6
Seal Gap
Hearth
Extension
Seal Gap
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MANTELS
A mantel may be installed if desired (see Figure 4).
Woodwork such as wood trims, mantels or any other
combustible material projecting from the front face
must not be placed within 12" of the fireplace open-
ing. Combustible materials above 12" and projecting
more than 1 / " from the fireplace must not be placed
1
2
less than 15" from the top opening of the fireplace
(NFPA STD 211, Sec. 7-3.3.3).
Mantels or any other combustible material also
may come up to the side edge of the black metal
face of the fireplace just as long as the projection
from the front face fall within the limit shown in
Figure 4.
1 / " Ref.
1
4
6"
Ref.
33°
3" Nom.
1 / " Max.
1

15" Min.
1" Min.
Fireplace
Opening
Top View of Fireplace
7.75"
SAFE ZONE
33°
Min. to
Perpendicular
Side Wall
1"
Figure 4 - Mantel Clearances to

Combustible Material

Combustible
Material
Safe
Zone for
Projection of
Combustible
Materials
Upper
Section of
Fireplace
FIREBOX
3" Max.
4.5"
Combustible
Material Must
Not Overlap
Front Face
109493-01K