OSB or plywood? Learn the differences in strength, moisture performance, cost and best uses for wall sheathing, roofs and subfloors, plus what CSA marks to look for in Canada.
What they are
Oriented strand board (OSB) is made from wood strands pressed and bonded in cross-oriented layers. Plywood is made from thin wood veneers glued together with the grain of each layer running at right angles to the next. Both are commonly sold in 4 × 8 ft (1220 × 2440 mm) sheets.
Where OSB is a great choice
- Wall and roof sheathing
- Subflooring in dry, protected conditions
- Projects where value matters, since OSB is typically the more economical panel
Where plywood is a great choice
- Areas that may see moisture swings during construction
- Exposed edges and finished surfaces, thanks to a smoother, more uniform face
- Cabinetry, shop projects and furniture using sanded grades
Moisture and cold weather
Both panels should be kept dry and protected on the job site. OSB edges can swell if they stay wet for long periods, while plywood tends to dry out and recover more readily. In winter, store sheets flat and covered, and leave a 3 mm (1/8 in) gap between panel edges so they can expand and contract.
Look for the CSA mark
In Canada, structural panels are made to CSA standards. Look for the CSA stamp on the panel: CSA O325 covers construction sheathing, CSA O121 covers Douglas fir plywood and CSA O151 covers Canadian softwood plywood.
Thickness, grade and snow loads
Panel thickness and span rating depend on rafter or joist spacing, the application and, for roofs, the snow load for your location. Tell us what you are covering and at what spacing, and we will match the panel to the job.
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