Credit: iLevel by Weyerhaeuser
OSB panels, such as these by iLevel by Weyerhaeuser, dominate the production home building market. They're used as roof and wall sheathing, as well as subfloors.
Versatile. In order to adapt to certain applications, OSB manufacturers can essentially just tweak the recipe for their product. Chris Degnan, marketing director of strand technologies at iLevel by Weyerhaeuser, says OSB “can be made in different formulations to suit various climates and budgets. This is especially important for floor panels, since OSB resists buckling and helps provide a flat and stable floor.”
Available in large sizes. Plywood can be produced in lengths from 8 feet to 10 feet, but that’s pretty much it. OSB, on the hand, says APA’s Adair, can be produced in panels up to 8 feet wide and in lengths of up to 16 feet. Some manufacturers say even 24 feet is possible. This is mainly due to production. An OSB plant can easily adjust to make longer boards, while plywood producers are limited by tree sizes.
Consistent. Anyone who has worked with OSB knows that the panels are dense and solid throughout the product. This is due to the manufacturing process. Consistent-sized thin wood strands are mixed with wax and adhesive and compressed with up to 1,100 pounds per square inch. Approximately 50 layers of strands make one sheet of OSB, according to HUD’s Partnership for Advancing Technology in Housing (PATH). “There are no soft spots such as those that can occur in plywood,” PATH says on its Website.
Good shear strength. “OSB is stronger than plywood in shear,” says a report by the Building and Construction Technology program at University of Massachusetts--Amherst. “Shear values, through its thickness, are about two times greater than plywood. This is one of the reasons OSB is used for webs of wooden I-joists.”
Resource-efficient. OSB is generally considered a resource-efficient product because of how it’s made. “OSB panels can be manufactured from a wide range of fast-growing species and from relatively small trees,” APA writes on its Website. The process uses the maximum amount of wood fiber from each tree, the group adds. The trees are often farm-raised, PATH adds, which reduces the demand for old growth timber.
Affordable. You don’t have to be a genius to figure this out. A simple trip to the average lumberyard or home supply store is all it takes to realize that OSB is almost always cheaper than plywood. “It can be $3 to $5 a panel less expensive than plywood,” PATH writes. “For a typical 2,400 square foot home, OSB will save about $700 if used as the subfloor, sheathing, and roof decking instead of plywood."
Credit: LP Building Products
LP Building Products has been making OSB structural panels for more than 30 years. The company says it can formulate panels to meet a variety of needs, uses, and locations.
Heavy. Depend on your point of view, OSB’s relative density could be seen as a bad thing. According to APA’s Website, a 23/32 plywood panel weighs 2.2 pounds per square foot compared to 2.4 pounds for an OSB panel of the same thickness. Atlanta-based Georgia Pacific, which manufactures both types of panels, says on its site that “although weights vary by species, on average, the weight of Southern yellow pine plywood is lighter than Southern yellow pine OSB.” The company continues: “Plywood is approximately 15% to 19% lighter than OSB. While the additional weight of OSB does not mean increased strength, it just means that it is heavier to handle on the job. In addition, OSB's higher weight means higher thermal conductivity (thus slightly less R value) than plywood.”
Lower moisture tolerance. Early on in its existence, OSB had a problem with moisture. (It should also be noted that plywood had similar performance problems with moisture early on its existence). “OSB used to swell a great deal or it could have taken market share faster,” Boise’s Mary Jo Nyblad says. “But manufacturers have improved the performance of the product.” Though third-party sources agree that the product’s moisture tolerances have greatly improved, many say it still does not perform as well as plywood. Georgia Pacific says that when plywood is exposed to moisture it swells evenly throughout the panel and returns to its nominal thickness as the wood dries. “OSB will remain swollen to some degree after it dries because the panel will still have the higher ‘compaction ratio’ that was present as of the date of manufacture,” the company says.
Prone to swelling edges and telegraphing. Even though manufacturers now use better adhesives and resins in OSB, the products’ edges are still susceptible to swelling once they are cut in the field. “The major disadvantage of OSB is that if it gets exposed to significant amounts of water or moisture, the edges expand by up to 15% ... especially if they are cut edges. This swell will then telegraph onto the shingles or some flooring," according to PATH.
Lower perceived value. Despite the fact that plywood and OSB meet the same performance requirements, the average consumer assumes OSB is an inferior product based on its look. “Many consumers are concerned when they see oriented strand board (OSB) being installed in their home,” according to PATH. “Because it costs less and looks different than plywood, they feel like they are getting a lower quality product, or that their contractor is trying to pull something on them. You need not worry; in many applications OSB has a comparable quality to plywood.”