Stellar reputation. Builders know and love plywood, and they trust its proven performance, whether they use this product or not. It’s the panel of choice for most DIY projects and can be found in a variety of applications throughout the home. To the average home buyer, it looks like real wood. It’s available in a wide variety of appearances, ranging from construction-grade products that are used for sheathing and underlayment to smooth panels for furniture and finish-grade work.
Strong and stiff. Plywood’s main attribute is that it’s stiff, strong, and durable. Citing an APA technical document, Georgia Pacific says “plywood panel bending stiffness is 10% greater than OSB at equal joist spacing.” This, the company says, results in stiffer floors that are less likely to be soft and springy.
Good moisture resistance and fast drying times. Clarence Young, vice president and general manager of Georgia Pacific’s structural panels business, says that even though OSB’s water absorption has improved, plywood overall is highly moisture tolerant and dries faster than OSB when it does get wet. Georgia Pacific now offers DryPly subfloor that has been treated to be even more moisture resistant. “It offers up to 40% less water absorption [during the normal construction cycle than uncoated plywood],” Young says.
Excellent as an underlayment. Though APA says the products are equal structurally, different flooring manufacturers recommend plywood under their products. “If you are installing a tile floor, the National Tile Contractors Association recommends that you not use OSB as a subfloor or underlayment because of the potential that swollen edges will weaken the tiles,” PATH writes.
The Building and Construction Technology program at University of Massachusetts Amherst says the Resilient Floor Covering Institute also recommends plywood over OSB under vinyl sheet-flooring. “[The Resilient Floor Covering Institute] installation specifications recommend plywood as an underlayment material,” the group says on its Website. ”OSB is acceptable as a subfloor material. Manufacturers have not seen a deluge of failures due to the use of OSB under resilient flooring. However, they have received complaints of edge swelling that has telegraphed through their flooring products. Manufacturers feel more comfortable guaranteeing their products when they are installed over plywood.”
More expensive than OSB. Though pricing for both OSB and plywood can sometimes be very similar depending on the market or region of the country, plywood generally costs more. Differential pricing hasn’t changed much over the years, Young says, but the difference itsef is noticeable. For example, at the time of this writing, Georgia Pacific says retail pricing in Atlanta is $5.22 sheet of 7/16-inch OSB and $10.97 per sheet for 3-ply plywood.
Panel voids. To make plywood, manufacturers shave thin sheets of veneer from a log. Once these sheets have been dried, the manufacturer applies adhesives and arranges the sheets alternating 90 degrees to each other and applies heat and pressure. The cross lamination of the sheets give the boards their strength, stiffness, and helps with expansion and contraction. But sometimes sheets have weak spots, which results in core voids in the panels. This can lead to reduced nail holding effectiveness. A quick glance on the edges of plywood, and the voids are often noticeable.
Limited sizes. Most builders get along fine with 4-by-8-foot plywood sheets, but that's also because they have to. Sometimes a large sheet could make life easier, but Young says more than 90% of plywood plants produce this basic size.
Nigel Maynard is senior editor for products at BUILDER magazine.