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. [1] OSB may have a rough and variegated surface with the individual strips of around 2.5 cm × 15 cm (1.0 by 5.9 inches), 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".
OSB is a material with favorable mechanical properties that make it particularly suitable for load-bearing applications in construction. [2] It is now more popular than plywood, commanding 66% of the North American structural panel market. [3] The most common uses are as sheathing in walls, flooring, and roof decking. For exterior wall applications, 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.
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). [4]
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. [5] 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. [6] 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. Individual layers can also vary in thickness to give different finished panel thicknesses; typically, a 15 cm (5.9 in) layer will produce a 15 mm (0.59 in) panel thickness[ citation needed ]. 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 world's OSB is made in the United States and Canada in large production facilities.
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. [7] Strand board can also be made from bagasse.
In 2005, Canadian production was 10,500,000 m2 (113,000,000 sq ft) (3⁄8 in or 9.53 mm basis) of which 8,780,000 m2 (94,500,000 sq ft) (3⁄8 inch) were exported, almost entirely to the United States. [8] In 2014, Romania became the largest OSB exporting country in Europe, with 28% of the exports going to Russia and 16% to Ukraine. [9]
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. [10] When tested to failure, OSB has a greater load-bearing capacity than milled wood panels. [11] It has replaced plywood in many environments, especially the North American structural panel market.
While OSB does not have a continuous grain like a natural wood, it does have greater strength on its long axis because more of the component grains are oriented in this direction. This can be seen by observing the alignment of the surface wood chips.
All wood-based structural use panels can be cut and installed with the same types of equipment as for solid wood.
The resins used to create OSB [12] have raised questions regarding the potential for OSB to emit volatile organic compounds such as formaldehyde. 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" OSB panels, use isocyanate resins that do not contain formaldehyde and are considered nonvolatile when cured. [13] Industry trade groups assert that formaldehyde emissions from North American OSB are "negligible or nonexistent". [14]
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.
Five grades of OSB are defined in EN 300 in terms of their mechanical performance and relative resistance to moisture: [2]
Plywood is a composite material manufactured from thin layers, or "plies", of wood veneer that have been stacked and glued together. It is an engineered wood from the family of manufactured boards, which include plywood, medium-density fibreboard (MDF), oriented strand board (OSB), and particle board.
Engineered wood, also called mass timber, composite wood, human-made wood, or manufactured board, includes a range of derivative wood products which are manufactured by binding or fixing the strands, particles, fibres, or veneers or boards of wood, together with adhesives, or other methods of fixation to form composite material. The panels vary in size but can range upwards of 64 by 8 feet and in the case of cross-laminated timber (CLT) can be of any thickness from a few inches to 16 inches (410 mm) or more. These products are engineered to precise design specifications, which are tested to meet national or international standards and provide uniformity and predictability in their structural performance. Engineered wood products are used in a variety of applications, from home construction to commercial buildings to industrial products. The products can be used for joists and beams that replace steel in many building projects. The term mass timber describes a group of building materials that can replace concrete assemblies.
Medium-density fibreboard (MDF) is an engineered wood product made by breaking down hardwood or softwood residuals into wood fibre, often in a defibrator, combining it with wax and a resin binder, and forming it into panels by applying high temperature and pressure. MDF is generally denser than plywood. It is made up of separated fibre but can be used as a building material similar in application to plywood. It is stronger and denser than particle board.
Phenol formaldehyde resins (PF) are synthetic polymers obtained by the reaction of phenol or substituted phenol with formaldehyde. Used as the basis for Bakelite, PFs were the first commercial synthetic resins. They have been widely used for the production of molded products including billiard balls, laboratory countertops, and as coatings and adhesives. They were at one time the primary material used for the production of circuit boards but have been largely replaced with epoxy resins and fiberglass cloth, as with fire-resistant FR-4 circuit board materials.
A structural insulated panel, or structural insulating panel, (SIP), is a form of sandwich panel used in the construction industry.
Glued laminated timber, commonly referred to as glulam, is a type of structural engineered wood product constituted by layers of dimensional lumber bonded together with durable, moisture-resistant structural adhesives so that all of the grain runs parallel to the longitudinal axis. In North America, the material providing the laminations is termed laminating stock or lamstock.
Masonite is a type of hardboard made of steam-cooked and pressure-molded wood fibers in a process patented by William H. Mason.
Pressed wood, also known as presswood, is any engineered wood building and furniture construction material made from wood shavings and particles, sawdust or wood fibers bonded together with an adhesive under heat and pressure. This makes it different from densified wood, which is solid wood that has been compressed to increase its strength and possibly modify other properties.
Particle board, also known as particleboard or chipboard, is an engineered wood product, belonging to the wood-based panels, manufactured from wood chips and a synthetic, mostly formaldehyde based resin or other suitable binder, which is pressed under a hot press, batch- or continuous- type, and produced. Particle board is often confused with oriented strand board, a different type of fiberboard that uses machined wood flakes and offers more strength.
Hardboard, also called high-density fiberboard (HDF), is a type of fiberboard, which is a pressed wood or engineered wood product. It is used in furniture and in the construction industry.
Laminated veneer lumber (LVL) is an engineered wood product that uses multiple layers of thin wood assembled with adhesives. It is typically used for headers, beams, rimboard, and edge-forming material. LVL offers several advantages over typical milled lumber: Made in a factory under controlled specifications, it is stronger, straighter, and more uniform. Due to its composite nature, it is much less likely than conventional lumber to warp, twist, bow, or shrink. LVL is a type of structural composite lumber, comparable to glued laminated timber (glulam) but with a higher allowable stress. A high performance more sustainable alternative to lumber, Laminated Veneer Lumber (LVL) beams, headers and columns are used in structural applications to carry heavy loads with minimum weight.
Urea-formaldehyde (UF), also known as urea-methanal, so named for its common synthesis pathway and overall structure, is a nontransparent thermosetting resin or polymer. It is produced from urea and formaldehyde. These resins are used in adhesives, plywood, particle board, medium-density fibreboard (MDF), and molded objects. In agriculture, urea-formaldehyde compounds are one of the most commonly used types of slow-release fertilizer.
Wood glue is an adhesive used to tightly bond pieces of wood together. Many substances have been used as glues. Traditionally animal proteins like casein from milk or collagen from animal hides and bones were boiled down to make early glues. They worked by solidifying as they dried. Later, glues were made from plant starches like flour or potato starch. When combined with water and heated, the starch gelatinizes and forms a sticky paste as it dries. Plant-based glues were common for books and paper products, though they can break down more easily over time compared to animal-based glues. Examples of modern wood glues include polyvinyl acetate (PVA) and epoxy resins. Some resins used in producing composite wood products may contain formaldehyde. As of 2021, “the wood panel industry uses almost 95% of synthetic petroleum-derived thermosetting adhesives, mainly based on urea, phenol, and melamine, among others”.
Fiberboard or fibreboard is a type of engineered wood product that is made out of wood fibers. Types of fiberboard include particle board or low-density fiberboard (LDF), medium-density fiberboard (MDF), and hardboard or high-density fiberboard (HDF).
Waferboard belongs to the subset of reconstituted wood panel products called flakeboards. It is a structural material made from rectangular wood flakes of controlled length and thickness bonded together with waterproof phenolic resin under extreme heat and pressure. The layers of flakes are not oriented, which makes it easier to manufacture. Waferboard is used as a material to build cheap furniture. This type of furniture is usually laminated.
A cement board is a combination of cement and reinforcing fibers formed into sheets, of varying thickness that are typically used as a tile backing board. Cement board can be nailed or screwed to wood or steel studs to create a substrate for vertical tile and attached horizontally to plywood for tile floors, kitchen counters and backsplashes. It can be used on the exterior of buildings as a base for exterior plaster (stucco) systems and sometimes as the finish system itself.
Building insulation materials are the building materials that form the thermal envelope of a building or otherwise reduce heat transfer.
Rigid panel insulation, also referred to as continuous insulation, can be made from foam plastics such as polyurethane (PUR), polyisocyanurate (PIR), and polystyrene, or from fibrous materials such as fiberglass, rock and slag wool. Rigid panel continuous insulation is often used to provide a thermal break in the building envelope, thus reducing thermal bridging.
Cross-laminated timber (CLT) is a subcategory of engineered wood panel product made from gluing together at least three layers of solid-sawn lumber. Each layer of boards is usually oriented perpendicular to adjacent layers and glued on the wide faces of each board, usually in a symmetric way so that the outer layers have the same orientation. An odd number of layers is most common, but there are configurations with even numbers as well. Regular timber is an anisotropic material, meaning that the physical properties change depending on the direction at which the force is applied. By gluing layers of wood at right angles, the panel is able to achieve better structural rigidity in both directions. It is similar to plywood but with distinctively thicker laminations.
Oriented structural straw board (OSSB) is an engineered board that is made by splitting straw and formed by adding methylene diphenyl diisocyanate (MDI) and then hot compressing layers of straw in specific orientations. Research and development for OSSB panels began in the mid 1980s and was spearheaded by the Alberta Research Council, Canada.
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