OSB-production before the press
Oriented strand board, or OSB, or waferboard, or Sterling board (UK), is an engineered wood product formed by layering strands (flakes) of wood in
specific orientations. In appearance it may have a rough and variegated surface with the individual strips (around 2.5 by 15 cm
(~1 inch by ~6 inches) each) lying unevenly across each other.
Manufacturing
It is manufactured in wide mats from cross-oriented layers of thin, rectangular wooden strips compressed and bonded together
with wax and resin adhesives (95% wood, 5% wax and resin). The layers
are created by shredding the wood into strips, these are sifted and then oriented on a belt or wire cauls. The mat is made in a
forming line, the layers are built up with the external layers aligned in the panel's strength axis with internal layers
cross-oriented. The number of layers placed is determined partly by the thickness of the panel but is limited by the equipment
installed at the manufacturing site, however individual layers can also vary in thickness to give different finished panel
thicknesses. Typically a 15 cm layer will produce a 15 mm panel thickness. The mat is placed in a thermal press to compress the
flakes and bond them by heat activation and curing of the resin that has been coated on the flakes. Individual panels are then
cut from the mats into finished sizes. Most of the worlds OSB is made in the USA and
Canada in large production facilities. The largest production facilities can make over
1,000,000,000 square feet of OSB per year.
Properties
Different qualities in terms of thickness, panel size, strength, and rigidity can be imparted to the OSB by changes in the
manufacturing process. OSB panels have no internal gaps or voids, and are water-resistant, although they do require additional
membranes to achieve impermeability to water and are not recommended for use as an exterior. The finished product has similar
properties to plywood, but is uniform and cheaper.[1] It has replaced plywood in many environments, especially the North American structural panel market.
The most common uses are as sheathing in walls, floors, and roofs.
While OSB does not have a continuous grain like a natural wood, it does have a specific axis of strength. This can be seen by
observing the alignment of the surface wood chips. The most accurate method for determining the axis of strength is to examine
the ink stamps placed on the wood by the manufacturer.
All wood-based structural use panels can be cut and installed with the same ease and types of equipment used with solid wood.
In 2001, 19.4 million m³ of OSB panel was produced in the US. The US is Canada's largest OSB market, receiving 98% of its export
product in 2005.[2]
Some manufacturers may treat the wood chips with various borate compounds which are toxic to
termites, wood boring beetles, molds, and fungus but not mammals in applied doses.
Buyers are recommended to seek borate modified wood products for construction, particularly in warm moist climates.
Environmental Impact
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The neutrality of this section is disputed.
Please see the discussion on the talk page. |
There is some debate over the environmental impact of OSB. It allows producers to use tree species such as aspen or poplar that are unfit for standard veneer plywood or lumber. The
production method uses almost all the wood of the harvested trees, and small, young trees and lower quality fast growing species
can be used. Due to the type of resins used in wood-based structural use panels like OSB, they emit very low levels of
formaldehyde. The emission levels have been found to be not more than 10% of the criteria
of key national standards.
Current Class Action Suit
A class action suit has been filed against several OSB manufacturers alleging price
fixing. [3]
See also
References
- ^ Choosing Between
Oriented Strandboard and Plywood
- ^ Review of
Canadian Structural Panel Market
- ^ Law firm, Vancouver Sun
External Links
Manufacturers
Borate
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