17
Installation Planning
Wall Finish
Non-Combustible Materials Speci
fi
cations
Material which will not ignite and burn. Such materials
are those consisting entirely of steel, iron, brick, tile,
concrete, slate, glass, or plasters, or any combination
thereof.
Materials that are reported as passing ASTM E 136,
Standard Test Method for Behavior of Materials in a
Vertical Tube Furnace at 750 °C shall be considered non-
combustible materials.
Combustible Materials Speci
fi
cations
Materials made of or surfaced with wood, compressed
paper, plant
fi
bers, plastics, or other material that
can ignite and burn, whether
fl
ame proofed or not,
or plastered or unplastered shall be considered
combustible materials.
Non-Combustible Cement Board
The LX1
fi
replace requires a 1/2” [13 mm] thick non-
combustible cement board to be used as a wall surface
as indicated in
“Clearances to Combustibles” on page 13
.
This is generally de
fi
ned as the area from the bottom
of the
fi
replace’s opening to the height of the stando
ff
s
(whether or not they are used).
Extending the cement board well beyond the minimum
will help avoid cracking due to di
ff
erential expansion of
materials.
Pre-drill cement board with oversized holes and do
not over-tighten screws to avoid cracking due to heat
expansion.
Standard gypsum wall board may be used beyond the
required perimeter of the cement board.
Preventing Cracking Wall Finishes
The HeatShift Duct Kit reduces the wall temperatures
and minimizes the possibility of cracking wall
fi
nishes.
If a clean
fi
nish with no tile, etc, is desired, joints in the
cement board and the transition to gypsum board
will require special attention if future cracking is to
controlled.
Shrinkage and di
ff
erential movement of the framing
and non-combustible wall board can transmit cracking
through to tiles, etc.
Be aware that temperatures on the non-combustible wall
surface above the appliance can exceed 200°F.
Below are some tips on how best to avoid any cracking:
• Allow materials to dry thoroughly before
fi
nishing the wall. Cement board has the ability to
absorb up to 30% of its weight in water and may
shrink as much as 1/8” over a 48” length when
drying from a saturated condition. Running the
fi
replace before
fi
nal
fi
nishing will help drive out
moisture.
• Always pre-drill screw holes through cement
board and use screws with self-milling head.
• Always use tape over joints.
• Behind joints, double up studs or use studs
“on the
fl
at” to add extra support to the
joint. Adhesive on the backside of wall board
behind any joints can help control di
ff
erential
movement.
• Use multiple, thinner coats of joint compound
and allow to dry thoroughly between coats.
• Ensure framing materials are dry.
• After
fi
nishing the wall, introduce heat gradually
to slowly dry any excess moisture rather than
drying too fast.
• Avoid notching cement board or tiles around
corners of window openings. Instead, provide a
joint that intersects the corner.
Cracks
Provide joints
either here or
here
