Wood Handbook, Wood as an Engineering Material

the predominant wood species used. As the industry learned
to control strand size, placement, and orientation, the per-
formance and utility of OSB products improved to the
point that their performance was similar to that of structural
plywood. As a result, product acceptance and the industry
expanded as OSB began to replace softwood plywood in
construction applications.

Raw Materials

In North America, aspen is the predominant wood used
for OSB. Species other than aspen, such as Southern Pine,
spruce, birch, yellow-poplar, sweetgum, sassafrass, and
beech, are also suitable raw materials for OSB production.
High-density species such as beech and birch are often
mixed with low-density species such as aspen to maintain
panel properties (Bowyer and others 2007).

Manufacturing Process

To manufacture OSB, debarked logs are sliced into long,

thin wood elements called strands. The strands are dried,

blended with resin and wax, and formed into thick, loosely

consolidated mats that are pressed under heat and pressure

into large panels. Figure 11–8 shows an OSB manufactur-

ing process. A more detailed description of each individual

manufacturing step follows.

During stranding, logs are debarked and then sent to a

soaking pond or directly to the stranding process. Long log

disk or ring stranders are commonly used to produce wood

strands typically measuring 114 to 152 mm (4.5 to 6 in.)

long, 12.7 mm (0.5 in.) wide, and 0.6 to 0.7 mm (0.023 to

0.027 in.) thick. Green strands are stored in wet bins and

dried in a traditional triple-pass dryer, a single-pass dryer, a

Figure 11–6. Typical grade stamps for plywood and OSB. (Courtesy of

TECO, Sun Prairie, Wisconsin, and APA–The Engineered Wood Associa-

tion, Tacoma, Washington. Used by permission.)

General Technical Report FPL–GTR– 190