Installation Manual - CertainTeed

CertainTeed WeatherBoards Fiber Cement Siding Installation Manual
Section 8:
Wall Preparation
and Sheathing
Before installing WeatherBoards Fiber Cement Siding,
review and comply with all local building codes and
regulations regarding wall construction, including the
proper use of framing (24" o.c. max.), weather-resistant
barriers, flashings, and other building materials
and systems.
If the sheathing is thicker than 1", consult the recommendations
below for installing fiber cement siding over
continuous insulation systems.
Plywood
or OSB
sheathing
Double wall
construction
Weatherresistant
barrier
Starter
strip
Single wall
construction
Lateral
brace
6" above
finished
grade
Double and Single Wall Construction
Weatherresistant
barrier
XXFiber cement siding should be applied over a rigid
sheathing that provides a smooth, flat surface that is no
more than 1" thick. Siding is an exterior cladding. It is
not a complete weather-resistant barrier, so be sure to
flash around all openings.
XXDo not install siding over questionable wall construction.
Irregularities in framing may become visible in the
finished application. To minimize the effect of uneven
walls, shim the wall as necessary.
XXIn accordance with best building practices, there
should be a gap between dissimilar materials.
Fiber cement should be separated from other
materials such as brick, stone, wood, and metal.
A 1/8" gap is recommended. Always caulk between
siding and dissimilar materials.
XXSiding is not a structural component of the wall. In
single-wall construction, lateral bracing is required
between the studs.
XXNon-structural materials such as underlayments, foam
board, or lathe/furring strips may not exceed 1" in
thickness without re-establishing a structural nailable
substrate (see below for details).
Sheathings
Structural
For best results, WeatherBoards Fiber Cement should
be installed over plywood, OSB, or comparable structural
sheathing. Fiber cement siding can be installed over
braced wood or steel studs in accordance with local
building codes.
Non-structural
Installing fiber cement siding over non-structural
sheathing, builder board, foam-type sheathings, and
gypsum board, such as CertainTeed‘s GlasRoc ®
Sheathing, is also acceptable if the siding boards are
fastened to structural framing. Non-structural sheathing
thickness in excess of 1" creates a condition where
WeatherBoards Fiber Cement siding products cannot be
properly attached to the existing structural surface (e.g.
framing members, steel studs, or structural sheathing).
The easiest way to meet the fastening requirements for
CertainTeed WeatherBoards Fiber Cement siding is to
install 3/4" structural sheathing over the non-structural
sheathing. However, the wall assembly must be designed
in such a way that the re-established structural fastening
surface (e.g. OSB, plywood, lathe strips, or 1x or 2x
framing lumber) is sufficient to meet the requirements of
ICC-ES Evaluation Report ESR-1668.
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