IN A BUILDING TRADE CHAT room last year, a contractor in Chicago posed a question: “What are your guys' thoughts?” began the query of ... let's call him Mr. No Clue. “We pretty much hate OSB,” No Clue continued. “We've found it to have problems with expansion, and it is softer underfoot than ply. But I have talked with many builders that pretty much only use OSB. Any thoughts?”
The answer, as No Clue found out, is much more complicated than the easy question he thought he posed. Unlike a pointless dispute about which is better, new Coke or Classic Coke (Classic) or the National League versus the American League (clearly the National), a debate about oriented strand board (OSB) and plywood has significant relevance that affects your business.
Is plywood in fact better than OSB? Like many things in this world, there is no easy answer: It depends on whom you're asking, where they build, what the climate there is like, and numerous other variables. What is certain, however, is that both products have their strengths and their loyalists who swear by their performance.
Board Stiff To understand OSB and plywood, it is important to recap the history of each product and how they are made. Plywood, which appeared around the turn of the 20th century, is the granddaddy of structural panels. According to the Tacoma, Wash.–based APA-The Engineered Wood Association, the product is comprised of thin sheets of veneer that are covered with adhesive, laid in cross layers, and pressed together. Cross-laminating adjacent layers, the association says, makes plywood an extremely strong, lightweight, and versatile panel that is resistant to shrinking and expansion.
OSB, on the other hand, is the (relatively) new kid on the block. Appearing around the late '70s, the product now accounts for about 60 percent of the panel market, and the industry says its market share is still rising. About 10 percent to 15 percent heavier than plywood, OSB—which uses trees more efficiently—is made from 3- to 4-inch wood strands that are applied in layers and pressed together with resin. Much like plywood, APA says, the layers are oriented at right angles to one another for strength and stiffness.
Given their different composition, it is tempting to say that one is better than the other, but as far as APA is concerned, both are interchangeable for routine construction applications. “That's because both products, although different in composition and appearance, are manufactured according to the same performance standards,” APA writes. “These standards apply the same performance criteria to both products for their designated end uses—sheathing, single-layer flooring, and exterior siding.” If this were to be taken at face value, you could conceivably use either product and rest assured that the performance would be the same. If things were ever that simple, the debate would end there. But there is more to the story. Ask OSB and plywood manufacturers, and both groups are likely to tell you that its product is better. In many cases, a couple of these manufacturers make both products, which complicates things even more.
Good Woods “We don't ever say that OSB is not a good product,” says Chris H. Beyer, director of marketing services for Atlanta-based Georgia-Pacific Building Products, which makes both products. “But plywood is better. [Plywood] has performance benefits that are important, and it is more versatile, especially when you talk about flooring options.”
In a 2003 technical paper, Georgia-Pacific stated that plywood holds up better under excessive wettings, has an all-wood surface that results in better glue adhesion, and is 15 percent lighter than OSB so it puts less stress on the floor framing system. Beyer further states that plywood is more forgiving than OSB and also helps create a quieter floor. “Tests indicate that it holds nails better, too,” Beyer adds.
Arthur Rutenberg Homes in Southwest Florida is fiercely loyal to ply. “We have always used plywood,” says purchasing director Ron Tyre. “We build custom homes for low maintenance and for longevity, and we don't use OSB. It's just an inferior product to plywood.”
Dominic Jansen, technical director for the Ontario, Canada–based Structural Board Association, a group that represents OSB manufacturers throughout the world, disputes Beyer's claim that plywood holds nails better than OSB. “Both products have the same nail-holding characteristics,” Jansen says. Moreover, Jansen adds, OSB offers more control over the production process so panels can be 4 by 9, 4 by 10, even 8 by 16 feet. “With more houses having taller walls, OSB meets those builders' needs,” he says.
Nevertheless, OSB has had some growing pains, and manufacturers have had to overcome some issues and problems associated with the product. Mary Joe Nyblad, sales and marketing manager for structural panels at Boise, Idaho–based Boise Building Solutions, says OSB used to have a problem with edge swell when it got wet. The product was also slippery so there was potential for people to fall off roofs. Manufacturers now put a grid on the panels, which makes it slip resistant, and they are using better adhesives that take care of the swelling problem, she says.
Plywood manufacturers say OSB has a tendency to “telegraph” when used as sheathing under resilient flooring. In other words, whatever surface bumps and imperfections are in the subfloor will show through the finished flooring. OSB still does not hold up well when exposed to moisture for long periods. Neither does plywood, says Doug McNeill, marketing manager for Toronto-based Norbord Industries. “Plywood can behave just brutally when it gets wet, too,” he says. What about OSB's tendency to telegraph? “We do not recommend OSB as a finished subfloor for vinyl or sheet flooring,” McNeill says. “We recommend a separate smooth underlayment under the floor.”
John VavRosky, structural panel marketing manager for OSB producer Potlatch in Spokane, Wash., agrees that OSB has had some issues, such as its reputation for reacting negatively to water, but manufacturers have addressed most (if not all) of the problems. “We have figured out how to make a better product,” VavRosky says. “There is a lot of innovation taking place.” VavRosky says, for example, products have better resins and painted edges to resist swelling. He says manufacturers make higher-quality panels by adding more wax and resin. “The more wax and resin we add, the better the performance,” he explains. Furthermore, he says the product is more uniform, has no core voids, and is knot free compared to plywood, so more builders prefer to use it.
Until last May, when it sold its only OSB mill, Boise was one of a few manufacturers that produced both types of panels. Nyblad says that though the company now sells only plywood, it does not (and did not) proclaim one product better than the next. “They both meet the minimum requirements for Product Standards 195, so they will give you a safe structure,” she says. “OSB is a more rigid panel because it uses more glue. Plywood gives more and has more of a spring to it, but it is not better.”
So if the performance and strength rating for OSB and plywood are the same, how are builders making their decisions? Familiarity is one way. “People have a preference for plywood,” Nyblad explains. “Some grew up with the product, and it looks familiar to them.” OSB, she says, with its strands showing on the surface, is cheaper-looking to people. Perhaps this is one reason a June Georgia-Pacific survey concluded that 77 percent of the homeowners it surveyed prefer plywood over OSB. “The attractive appearance of plywood was cited as the main contributing factor in their decision to use plywood,” the company said.
Price Is Right In the end, none of that really matters: “The bottom line is that builders are going to use what's readily available and cost competitive,” VavRosky says. And price is one area where OSB has historically beaten plywood. Bill Langford at Jim Walters Homes in Tampa, Fla., seems to agree with that assessment. Langford says the company uses plywood sometimes but primarily uses OSB for the walls and roof. “Cost is the main reason,” he says. “Occasionally we have to replace the product due to rain, but we deal with it.”
OSB costs about $3 to $5 less per panel than plywood, which is a significant difference when you consider that a one-story house can have almost 180 to 200 panels for the roof and walls. In one Washington area lumberyard, a 4-by-8-foot, tongue-and groove OSB panel measuring 23/32 inches cost $24.99, while plywood of similar thickness and style cost $27.99. This is the kind of price difference that helped propel OSB to huge market gains in the '90s. McNeill agrees that cost has played a role, but says that's not the only thing. “Cost is a factor only if there is a long-term savings for the builder,” he says “[Builders] look for value, and there is value in OSB,” he continues. “If plywood were that good, why has the market swung toward OSB?” (According to APA, the total North American OSB production in 2003 was about 24 billion square feet compared to about 17 billion for plywood.)
In recent times, both OSB and plywood have become equally costly. The Wall Street Journal reported in August that the price of plywood and OSB had soared 24 percent since June 2003 for a number of reasons: the war in Iraq, China's building boom, robust domestic demand, wildfires, rebuilding efforts following Hurricane Isabel, a 27 percent tariff on Canadian imports, and the weak U.S. dollar. On top of that, APA is warning builders and contractors that imported plywood may be substandard. Field inspections conducted in Pennsylvania and Maryland reveal that panels had incomplete grade stamps and were inappropriate for the job. Such panels, APA says, could impact durability or compromise safety.
So all things considered, what does this mean? Several things, if you read between the lines. On one hand, you can use OSB or plywood for sheathing the roof, siding, and floors of your houses and rest assured that either product will perform admirably and up to code. On the other hand, if you are concerned that your rainy climate may damage your sheathing or your rough OSB will telegraph through the vinyl floor or that edge swelling may separate the ceramic tile, use plywood or use one of the many OSB products that now come with a smooth sanded finish or one of those that have a painted edge to reduce swelling. You could also base your decision on price, in which case, whichever product suits your bottom line is the bottom line.