Builders used solid board sheathing until the Portland Manufacturing Company made the first plywood in 1905. Those early structural plywoods were cross-laminated and heat- bonded using non-waterproof soybean glue and animal blood. Water tended to penetrate the natural resins and cause de-lamination. During World War II, waterproof synthetic resins were developed, and subsequently used to make plywood for the post-war housing boom. In 1963, Macmillan Bloedel began to produce "waferboard," a random composition of wafer-shaped wood chips pressed together with waterproof resin as a low-cost alternative to plywood.
Plywood is constructed using thin sheets of veneer peeled from a spinning log. The veneers follow the annual rings of the wood, providing strong, uniform grain direction. Plywood panels are formed by positioning the grain direction of each layer perpendicular to the next. The layers are then bonded together using synthetic resins placed between the plies, and compressed using a heated press. The plywood panel is formed using an odd number of layers to make the finished product structurally stable.
Waferboard is made of wafer-like wood chips made from logs. The wafers are randomly aligned to form a homogeneous mixture of waterproof resin and wood fiber that is compressed under heat to form a hard panel. Waferboard, sometimes called chipboard, is weaker and less stiff than plywood due to waferboard's lack of layered lamination and alternating grain direction. By 1989, most waferboard plants were producing a stronger product called oriented waferboard (OWB) that used the alternating lamination techniques of plywood production.
Oriented strandboard (OSB), a hybrid of waferboard and plywood, was first made in Clairmont, New Hampshire, in 1994. This engineered wood product has some of the characteristics of each of its predecessors and is often mistaken for waferboard. To make OSB, logs are ground into strands that are thinner than those found in waferboard. The strands are dried, mixed with wax and resin, and formed into mats. The mats are positioned so the wood strands in each mat run perpendicularly to each other before being hot-pressed into panels.
The performance guidelines published by the American Plywood Association consider OSB and plywood to be performance equals. The weights of the two products are similar. A 7/16-inch panel of OSB weighs 46 lbs. and a 1/2-inch sheet of plywood weighs 48 lbs. Waferboard is considerably lighter. Waferboard and oriented strandboard are both considered under the broad category of "flakeboards." OWB is stronger than waferboard but not as strong as OSB or plywood.
- University of Massachusetts; Building and Construction Technology: Choosing Between Oriented Strandboard and Plywood; Paul Fisette; 2005
- Environmental Protection Agency; Wood Products Industry: Waferboard/Oriented Strandboard Manufacturing
- American Plywood Association; Plywood -- The Original Engineered Wood Product
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