OSB (Oriented Strand Board)
OSB is an engineered wood panel manufactured from cross-oriented layers of wood strands bonded with resin under heat and pressure, commonly used for roof decking, wall sheathing, and subflooring.
Oriented Strand Board (OSB) has become the dominant sheathing material in modern construction, often preferred over traditional plywood due to its consistent quality and lower cost. OSB is manufactured by compressing multiple layers of wood strands with adhesive, with each layer oriented perpendicular to the next for maximum strength. This engineered process eliminates natural wood defects and provides uniform structural properties throughout the panel.
Why It Matters
OSB provides critical structural support and weather protection when properly installed. For roof decking, it creates a solid base for underlayment and shingles while resisting wind uplift. For wall sheathing, OSB braces the structure against racking and provides a nailing base for siding. Modern OSB includes tongue-and-groove edges for easier installation and enhanced performance. In Denver's climate, choosing proper thickness and ensuring proper installation with appropriate gaps for expansion is essential.
Common Applications
- Roof decking: 7/16-inch or 1/2-inch panels over rafters or trusses
- Wall sheathing: 7/16-inch panels over wall studs for structural bracing
- Subflooring: 23/32-inch tongue-and-groove panels over floor joists
- Rim boards: Vertical orientation at floor perimeters
- Temporary construction barriers and work surfaces
Related Terms
Underlayment
Underlayment is a water-resistant or waterproof barrier installed over roof decking before shingles, or a smooth layer placed over subflooring before finish floor installation.
Framing
Framing is the process of constructing the structural skeleton of a building using dimensional lumber or engineered wood to create walls, floors, and roof systems.
Flashing
Flashing is thin, waterproof material (typically metal or membrane) installed at vulnerable points in a building envelope to direct water away from joints, seams, and penetrations.