Oriented strand board
Oriented strand board (OSB) is a type of engineered wood, formed by adding adhesives and then compressing layers of wood strands (flakes) in specific orientations. It was invented by Armin Elmendorf in California in 1963.<ref>Template:Cite web</ref> OSB may have a rough and variegated surface with the individual strips of around Template:Convert, lying unevenly across each other, and is produced in a variety of types and thicknesses.
Oriented strand board is sometimes confused with chipboard, a synonym for particle board, whose "chips" are of a size that a lay person would likely describe as "particles".
Uses
OSB's mechanical properties make it suitable for load-bearing applications in construction.<ref name="osb-info1">Template:Cite web</ref> In North America, it is more popular than plywood, commanding 66% of the structural panel market in 2016.<ref>Template:Cite news</ref> The most common uses are as sheathing in walls, flooring, and roof decking. For exterior walls, panels are available with a radiant-barrier layer laminated to one side; this eases installation and increases energy performance of the building envelope. OSB is also used in furniture production.
Manufacturing
Oriented strand board is manufactured in wide mats from cross-oriented layers of thin, rectangular wooden strips compressed and bonded together with wax and synthetic resin adhesives.
The adhesive resins types used include: urea-formaldehyde (OSB type 1, nonstructural, nonwaterproof); isocyanate-based glue (or PMDI poly-methylene diphenyl diisocyanate–based) in inner regions with melamine-urea-formaldehyde or phenol formaldehyde resin glues at surface (OSB type 2, structural, water resistant on face); phenol formaldehyde resin throughout (OSB types 3 and 4, structural, for use in damp and outside environments).<ref>Template:Citation</ref>
The layers are created by shredding the wood into strips, which are sifted and then oriented on a belt or wire-mesh caul (a heated, ventilated support) and coated with the resin.<ref>Template:Cite book</ref> The layers thus built up are transferred to a forming line and cross-oriented so that strips on the external layers are aligned to the panel's strength axis, while the internal layers are perpendicular.<ref>Template:Cite book</ref> The number of layers placed is determined partly by the thickness of the panel, and is limited by the equipment used. Individual layers can also vary in thickness to give different finished panel thicknesses; typically, a Template:Convert layer will produce a Template:Convert panel thicknessTemplate:Cn. The mat is placed in a thermal press to compress the flakes and bond them by heat activation and curing of the resin. Individual panels are then cut from the mats into finished sizes. Most of the world's OSB is made in the United States and Canada in large production facilities.
Related products
Materials other than wood have been used to produce products similar to OSB. Oriented structural straw board is an engineered board made by splitting straw and formed by adding P-MDI adhesives and then hot compressing layers of straw in specific orientations.<ref>Template:Cite journal</ref> Strand board can also be made from bagasse.
Production
In 2005, Canadian production was Template:Convert (Template:Convert basis) of which Template:Convert (Template:Frac inch) were exported, almost entirely to the United States.<ref>Template:Cite web</ref> In 2014, Romania became the largest OSB-exporting country in Europe, with 28% of the exports going to Russia and 16% to Ukraine.<ref name="Fordaq">Template:Cite news</ref>
Properties
Adjustments to the manufacturing process can affect thickness, panel size, strength, and rigidity. OSB panels have no internal gaps or voids, and can be water-resistant, although they do require additional membranes to achieve impermeability to water and are not recommended for exterior use. The finished product has properties similar to plywood, but is uniform and cheaper.<ref>Template:Cite web</ref> When tested to failure, OSB has a greater load-bearing capacity than milled wood panels.<ref>Template:Cite web</ref> It has replaced plywood in many environments, especially the North American structural panel market.
All wood-based structural use panels can be cut and installed with the same types of equipment as for solid wood.
Health and safety
The resins used to create OSB have raised questions about their emission of volatile organic compounds such as formaldehyde,<ref>Template:Cite journal</ref> although industry trade groups assert that formaldehyde emissions from North American OSB are "negligible or nonexistent".<ref>Template:Cite web</ref> Urea-formaldehyde is more toxic and should be avoided in home use. Phenol-formaldehyde products are considered to be relatively hazard free. Some newer types of OSB, so-called "new-generation" panels, use isocyanate resins that contain no formaldehyde and are considered nonvolatile when cured.<ref>Template:Cite web</ref>
Some manufacturers treat the wood chips with various borate compounds that are toxic to termites, wood-boring beetles, molds, and fungi, but not mammals in applied doses.
In 2024, a hotel in Dublin, Ireland, lost its fire safety certificate after an inspection found fault with the composition of OSB in its flooring and walls.<ref>Template:Cite news</ref>
Types
Five grades of OSB are defined in EN 300 in terms of their mechanical performance and relative resistance to moisture:<ref name="osb-info1"/>
- OSB/0 – No added formaldehyde
- OSB/1 – General-purpose boards and boards for interior fitments (including furniture) for use in dry conditions
- OSB/2 – Load-bearing boards for use in dry conditions
- OSB/3 – Load-bearing boards for use in humid conditions
- OSB/4 – Heavy-duty load-bearing boards for use in humid conditions
See also
- Medium-density fibreboard, engineered board with much smaller flakes