Here is my documentation to support plywood being superior to osb. Opposing views are welcome and I know there are OSB supporters out there, so lets see why you choose that instead.
I got most of this information from a Georgia Pacific article on plywood versus OSB Versatility, Stiffness, Creep - edge swell.
Since they manufactured both products at the time, I feel it is a very reliable and unbiased source. I have many other supporting articles as well, but this is the main highlights.
Ed
OSB swell is generally greater than in plywood due to the release of compaction stress in OSB created during the pressing of wood chips into an OSB panel. Plywood that has swollen will return 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 comparison below, undertook by the APA, lists the thickness swell (in percent) using a water soak test.
Plywood Average swell= 6% to 8% depending on thickness
OSB Average swell= 10% to 15% depending on thickness
Over a period of time, when subjected to high humidity or a series of dramatic wetting events, OSB is more prone to panel swell than plywood especially at the edges. Panel swell is most noticeable along the edges where it is critical for flooring and roof sheathing to match-up as not to show through the flooring or roofing materials.
Research done by the USDA Forest Products Laboratory (Research Paper FLP-RP-574) shows that over an extended period of time, under low constant loads and temperature, and in high-humid conditions, OSB will sag or "creep" more than plywood.
Plywood OSB
50% RH Fractional creep values 1.4mm 1.7mm
85% 1.9mm 5.2mm
Cyclic RH 50%-85% 2.0mm 4.6mm
Long-term, plywood sags less than OSB in humid conditions. In humid areas with vented attics and crawl spaces, using plywood for roof and floor sheathing can reduce risk of sagging roofs and floors.
APA Technical Note N375B states that plywood panel bending stiffness is 10% greater than OSB at equal joist spacing. Panel bending stiffness is the capacity to resist deflection.
Density of plywood is 34-36 pounds per cubic foot compared to OSB at 38-42 pounds per cubic foot.
One 23/32" 4'x 8' plywood piece would weigh approximately 67 lbs.
One 23/32" 4'x 8' OSB piece would weigh approximately 78 lbs.
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.
Plywood and OSB: Screw withdrawal or holding ability.
Group 1 plywood, made from the strongest species of wood such as Southern Yellow Pine, holds screws better than OSB.
Plywood and OSB: Nail withdrawal or holding ability.
As shown in APA report T2001-3A, plywood generally has higher nail withdrawal values using plain-shank, ring-shank, and screw-shank nails, even though OSB has a higher density than plywood. The numbers below reflect dry test conditions. The numbers vary some when tested under dry to wet-redry conditions.
Withdrawal strength (lbs/in. penetration)
Plain Ring Screw
5/8" Plywood Mean: 79.7 316.3 83.7
23/32" OSB Mean: 67.6 281.5 63.9
Nail withdrawal strength measures the force to pull the embedded nail from the nailed parts.
After roof sheathing or sub floor panels are nailed to the framing, nails will remain in place better in plywood than OSB.
Under severe weather testing, plywood is shown to be more impact resistant than OSB. Plywood outperforms OSB in the South Florida Building Code (Dade and Broward Counties) mandated use of the "large missile" impact test for materials used in walls and roofs.
Plywood is more impact resistant than OSB. This provides resistance to flying objects in high wind situations. More impact resistance provides added durability against accidents caused by impact on floors, roofs, and walls on the inside and outside of the home.
“We don't ever say that OSB is not a good product,†says Chris H. Beyer, director of marketing services for 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.â€
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.
John VavRosky, structural panel marketing manager for former OSB producer Potlatch in Spokane, Wash., agrees that OSB has had some issues, such as its reputation for reacting negatively to water.
VavRosky says, for example, OSB products have better resins and painted edges to resist swelling.
A June 2004 Georgia-Pacific survey concluded that 77 percent of the homeowners it surveyed prefer plywood over OSB.
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.â€
Ed
I got most of this information from a Georgia Pacific article on plywood versus OSB Versatility, Stiffness, Creep - edge swell.
Since they manufactured both products at the time, I feel it is a very reliable and unbiased source. I have many other supporting articles as well, but this is the main highlights.
Ed
OSB swell is generally greater than in plywood due to the release of compaction stress in OSB created during the pressing of wood chips into an OSB panel. Plywood that has swollen will return 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 comparison below, undertook by the APA, lists the thickness swell (in percent) using a water soak test.
Plywood Average swell= 6% to 8% depending on thickness
OSB Average swell= 10% to 15% depending on thickness
Over a period of time, when subjected to high humidity or a series of dramatic wetting events, OSB is more prone to panel swell than plywood especially at the edges. Panel swell is most noticeable along the edges where it is critical for flooring and roof sheathing to match-up as not to show through the flooring or roofing materials.
Research done by the USDA Forest Products Laboratory (Research Paper FLP-RP-574) shows that over an extended period of time, under low constant loads and temperature, and in high-humid conditions, OSB will sag or "creep" more than plywood.
Plywood OSB
50% RH Fractional creep values 1.4mm 1.7mm
85% 1.9mm 5.2mm
Cyclic RH 50%-85% 2.0mm 4.6mm
Long-term, plywood sags less than OSB in humid conditions. In humid areas with vented attics and crawl spaces, using plywood for roof and floor sheathing can reduce risk of sagging roofs and floors.
APA Technical Note N375B states that plywood panel bending stiffness is 10% greater than OSB at equal joist spacing. Panel bending stiffness is the capacity to resist deflection.
Density of plywood is 34-36 pounds per cubic foot compared to OSB at 38-42 pounds per cubic foot.
One 23/32" 4'x 8' plywood piece would weigh approximately 67 lbs.
One 23/32" 4'x 8' OSB piece would weigh approximately 78 lbs.
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.
Plywood and OSB: Screw withdrawal or holding ability.
Group 1 plywood, made from the strongest species of wood such as Southern Yellow Pine, holds screws better than OSB.
Plywood and OSB: Nail withdrawal or holding ability.
As shown in APA report T2001-3A, plywood generally has higher nail withdrawal values using plain-shank, ring-shank, and screw-shank nails, even though OSB has a higher density than plywood. The numbers below reflect dry test conditions. The numbers vary some when tested under dry to wet-redry conditions.
Withdrawal strength (lbs/in. penetration)
Plain Ring Screw
5/8" Plywood Mean: 79.7 316.3 83.7
23/32" OSB Mean: 67.6 281.5 63.9
Nail withdrawal strength measures the force to pull the embedded nail from the nailed parts.
After roof sheathing or sub floor panels are nailed to the framing, nails will remain in place better in plywood than OSB.
Under severe weather testing, plywood is shown to be more impact resistant than OSB. Plywood outperforms OSB in the South Florida Building Code (Dade and Broward Counties) mandated use of the "large missile" impact test for materials used in walls and roofs.
Plywood is more impact resistant than OSB. This provides resistance to flying objects in high wind situations. More impact resistance provides added durability against accidents caused by impact on floors, roofs, and walls on the inside and outside of the home.
“We don't ever say that OSB is not a good product,†says Chris H. Beyer, director of marketing services for 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.â€
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.
John VavRosky, structural panel marketing manager for former OSB producer Potlatch in Spokane, Wash., agrees that OSB has had some issues, such as its reputation for reacting negatively to water.
VavRosky says, for example, OSB products have better resins and painted edges to resist swelling.
A June 2004 Georgia-Pacific survey concluded that 77 percent of the homeowners it surveyed prefer plywood over OSB.
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.â€
Ed
Comment