Acclimatize Siding Before Installing
One of the most stable softwoods, Western Red Cedar is nevertheless a natural material and it responds to the
environment. Cedar siding can swell or shrink as it gains or loses moisture to reach equilibrium with the moisture
content of the surrounding air. Ensuring that the moisture content of cedar siding is at equilibrium before it is installed
will minimize movement later on. Recommended moisture content for sidings are given in the table below.
| | Average | Individual Pieces |
| Most areas | 12% | 9-14% |
| Dry areas | 9% | 7-12% |
| Damp, warm coastal | >12% | 9-20% |
1) To calculate average, test 10% or more of pieces.
2) Source: Wood Handbook 1987.
The following procedures are suggested for different siding specifications:
Kiln Dried Clear Siding
Kiln dried siding products are the preferred choice for consistency, stability, paintability and overall performance.
These siding products have been dried at the mill to 12-15% moisture content. They are the most ready-to-use of all
siding products. If the siding has not been wetted prior to arrival on the job site it may be applied upon arrival except
in hot and dry conditions where 3 to 5 days of well ventilated storage away from direct sunlight is generally required.
If the siding has been wetted it must be separated and allowed to dry to the local equilibrium moisture content.
Dry Knotty Sidings
Some knotty sidings are air or kiln dried to less than 19% moisture content. These products should be acclimatized to
ambient moisture conditions by stacking the siding on evenly spaced, vertically aligned stickers in a dry storage area
for 7-10 days. More time may be required in damp or humid conditions.
Green (Unseasoned) Sidings
Unseasoned or green sidings have not been dried prior to delivery and require a longer time to acclimatize than
seasoned sidings. Separate the siding with vertically aligned stickers, keeping two pieces stacked face to face between
stickers and store in a well ventilated dry location for a minimum of 30 days, or longer in damp or humid conditions.
If specifying unseasoned siding, patterns such as channel, bevel and board-and-batten are recommended since these
allow for shrinkage. Narrower widths are also recommended since they move less overall than wider widths. Note the
WRCLA discourages the use of green sidings.