Q+A: Plywood versus OSB

Thanks for asking!

We are going to be starting construction right when the weather turns bad.  Should be use plywood instead of OSB for the floor, wall and roof sheathing?

Good question!  I definitely recommend using plywood instead of OSB (oriented strand board) for not only wet weather construction, but for construction in general for several reasons:

1.  Exterior grade plywood will withstand repetitive wetting and drying with little or no damage.  OSB also graded for exterior use is designed to withstand the weather.  The difference is that OSB is sealed on the edges with a special waterproofing.  When cut, the exposed cut edges can be prone to swelling or damage.  It is possible to seal all cut edges, but this typically is not done.  Therefore, plywood is a more reliable choice for wet weather construction for floor, wall, and roof sheathing.

2.  Plywood is more dimensionally stable when exposed to wet conditions.  OSB tends to swell when exposed to wet conditions for a long period of time and does not return to the original dimension.  Plywood, on the other hand, will return to its original dimension when it dries.

3.  Joints between the plywood or OSB panels need to account for expansion and contraction.  OSB tends to expands and contracts more than plywood.  If the joints between the panels are too tight, the panel can ‘oil-can’ effect and cause the siding or finish material to protrude with the panel.

Feel free to contact H2D at 206-370-4762 with questions!  We’d be happy to help you find the answer!


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