OSB, or “oriented standard board” and plywood are similar in appearance and sometimes interchangeable as a subflooring or sheathing material. Despite their similar qualities, building professionals and DIY builders would often prefer one over the other. How can two very similar wood products remain significantly different? Let’s dive in and figure it out.
Oriented standard board (OSB), is engineered wood panels made from compressed pieces of wood glued and pressed together. The wood used to make OSB is from fast-growing trees, the majority of which are harvested from tree farms and not from forests. OSB is not the same as chipboard or waferboard because OSB is designed to equal plywood in performance.
OSB is dense; a single sheet has as many as 50 strand layers compacted and pressed to the same thickness of regular plywood. However, this also means that OSB is slightly heavier than plywood in most cases. OSB is usually manufactured in long lengths (up to 16 feet or 4.9 meters).
OSB expands rapidly along the sides of the panel when exposed to water sources. Currently, OSB has grown to be a popular choice as sheathing and flooring materials because it is relatively cheap.
Plywood is manufactured by bonding three or more thin layers (called “plies”) of real wood; hence, thicker plywood is composed of more layers. It is a composite material where the grain of every other layer of wood is placed in the same direction. The grain of the layer in between is usually oriented at 90 degrees. Thicker plywood may have each layer oriented in 30-degree increments (e.g. 0, 30, 60, and 90 degrees). This rotation of the grain is called cross-graining and gives plywood many desirable qualities. It reduces the chance of plywood edges splitting and also limits the board from shrinking and expanding. Cross-graining gives plywood strength in all directions of the board.
OSB vs Plywood
So what’s the difference between OSB and plywood? DIY builders and construction experts agree that OSB and plywood can be interchanged in terms of usability. Despite similarities in this area, a few significant differences can still be considered when choosing between OSB and plywood.
OSB is combination of wood particles compacted and bound together by glue. Plywood is composed of three or more layers, or “plies,” of real wood. A single OSB can be composed of fifty strand layers of wood compacted together to produce a single panel with the same thickness as regular-sized plywood. On the other hand, a single plywood board is made of at least three thin layers of wood veneer pressed and glued together.
OSB takes a longer time to get soaked, but takes longer to dry as well. Plywood swells when it gets wet. However, it dries faster than OSB and goes back to its normal dimensions when dried. Production of OSB is more environment-friendly as the wood is sourced from tree farms that grow smaller, fast growing trees. Plywood is sourced through conventional methods of harvesting trees in the forest. This contributes to the fact that OSB can be cheaper than plywood.
|Composed of compacted wood particles/strands bound together by glue||Made of cross-grained, thin layers of wood veneer|
|Takes time to get soaked and also to dry out; long exposure to moisture causes edges to deform||Swells in long periods of water exposure but returns to original dimensions when dried|
Check out this YouTube video for more information about OSB and plywood as used as a subflooring material.