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 fireplace opening is required to protect combustible floor construction in front of fireplace. 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 material selected has a K factor of 0.25, such as glass fiber, the following formula would apply:
0.25x 1.0" = 0.30" thickness required
Thermal conductivity "K" of materials can be obtained from manufacturer or supplier of noncombustible material. If 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 hearth extension from shifting and seal gap between fireplace frame and hearth extension with a noncombustible material (see Figure 3).
WARNING: Hearth extension
is to be installed only as shown
in Figure 3.
Seal Gap
Fireplace Front
Ember Protector
NO |
|
Do Not Block Louver | Hearth |
| |
| Extension |
Fireplace Front | Seal Gap |
Elevated |
|
Ember Protector
Hearth Extension, Circulating Modes
Seal Gap
Fireplace Front
Ember Protector
Fireplace Front |
|
Raised Hearth |
|
Ember Protector | Hearth |
| |
| Extension |
Fireplace Front | Seal Gap |
Elevated |
|
Ember Protector |
|
Hearth Extension, Noncirculating Models
Figure 3 - Hearth Extension
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