Lennox Hearth C42 - Manual (Page 11)

Figure 8
11
NOTE: DIAGRAMS & ILLUSTRATIONS ARE NOT TO SCALE.
The screws should be driven through the cement board into the outer
metal skin of the fireplace. The sheetrock (drywall) is then butted up
to the cement board. The sheetrock above the fireplace should also be
fastened to the fireplace by driving screws into the outer metal skin of
the fireplace.
Facing Less Than 1” Thick: If the combined thickness of the facing
material (eg. 3/8” [9.5 mm] thick ceramic tile and 1/2” [13 mm] thick
cement board) is less than 1” (25mm), then the tile can be placed behind
the fireplace face (see below).
Facing Installation Considerations
Non-combustible cement board (such as Wonderboard, Durock, or
Hardybacker) must extend 10” (254 mm) above the 1” (25 mm) top
reveal and a minimum of 3” (76 mm) from each side reveal (see Figure
8). This cement board may be 1/4” (6.3 mm) thick or greater, but would
normally be the thickness of the drywall - for example 1/2” (13 mm).
The cement board may be fastened by drywall screws.
Cement Board
3/8” Tile and 1/2” Cement
Board Behind Fireplace Face
Cement Board - a minimum
of five inches wide.
Sheetrock
1” Reveal
5” (127mm)
Minimum
Sheetrock
3” (76mm)
Minimum
Cement Board - Minimum
of 3” (76mm) Wide
10” (54mm)
Minimum
3/8” (9.5mm) Tile and 1/” (1.7mm) Cement Board
Behind Fireplace Face
Sheetrock
Cement Board
1” Reveal
(5mm)
Sheetrock