Understanding OSB
OSB, or Oriented Strand Board, an engineered panel made from wood, is finding wider applications in various industries and markets. This structural panel consists of long wood strands, approximately 18 mm in thickness, bonded by waterproof and heat-cured synthetic resin-based adhesives.
Typical construction involves three cross-directional layers. The bottom and top layers have a longitudinal wood strand orientation. The core layer has a perpendicular strand orientation.
Fabrication processes can include tests for density, bending and moisture content. The result is a lightweight, strong and dimensionally stable high-density panel without voids, knotholes, laps or gaps that resists delamination, deflection, warping or thermal expansion.
More recent efforts to reduce known toxic outgassing from standard adhesives have also led to the employment of formaldehyde-free alternative adhesives, like soy-based technology and formaldehyde-free PMDI glue, as a means to increase safety.
Applications for OSB
Principle industries involved include:
Construction
Packaging
Interior Furnishings
Applications for OSB include single-layer flooring, subflooring, roof and wall sheathing, deck and ceiling sheathing, web material between I-joists, structural insulated panels, industrial containers and furniture.
In new construction, oriented strand board represents the majority of wood-based structural paneling.
In 2019, wall-sheathing OSB, which tends to run at 3/8” or 7/16” in thickness, amounted to approximately two-thirds of wall-sheathing applications. OSB sheathing is designed to offer enough racking strength to support corner bracing demands and absorb the impacts of wind, seismic stress or thermal expansion.
OSB is also a major incorporation in roofing applications, particularly roof sheathing, which also made up about two-thirds of OSB consumption in 2019. Roof sheathing panels tend to run 7/16” or 15/32” in thickness, with 3/8” in low-snow areas. In addition to racking strength, these panels can also support gravity loads of snow, people or finish roofing.
OSB can also serve as both an underlayment and a subfloor in single-layer flooring systems. Wood structural panels suitable for flooring are typically 23/32” thick and can come with tongue-and-groove edges to help guard against uneven wear.
OSB Product Grades
There are four market-type splits for OSB, defined by the EN 300 European standards for structural use. These standards establish terms, specific requirements and classification for OSB products. The four OSB grades are:
OSB/1 – Boards for general applications and for equipment or interior furniture in dry environments
OSB/2 – Load-bearing panels for dry-environment applications
OSB/3 – Load-bearing panels for humid environments
OSB/4 – Load-bearing panels for heavy-duty applications in humid environments
