OSB vs. Plywood
Saw this posted on another forum I frequent, and thought it would be relevant to every one here as well.
- A Contractor Talk forum had this comparison:
Here are the highlights to support my utilization of CDX instead of OSB.
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.
50% RH Fractional creep values
85% RH Fractional creep values
Cyclic RH 50%-85% creep values
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
Mean: 79.7 316.3 83.7
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.
Check out this link for more information.
I hate everything about working with OSB when it comes to the haunt. I would rather pay more for the plywood.
OSB sucks....I think for the most part you are preaching to the chior. I have a few OSB panels that have hung around for five years or so, but almost all of mine are plywood now. My crew and I hate the OSB panels for several reasons. The main one is that they are a bitch to carry. Roughtly three times the weight of the plywoo panels. My show goes up and down each year so weight is definitely a factor.
I'd never heard of the word 'creep' in conjunction with building terms..
Kinda funny, considering the application here..:D wait! we WANT ~creepy~ plywood don't we?? :D
We've gone to all plywood over the years too.. Our original walls were OSB.
How much should a 4x8 panel cost to construct??
I'm not sure, but...
I once had some really old plywood I removed and then used again and it might have been as old as going back to the 1930's?
Talk about solid! And what incredible glue too!
My kitchen table is that old the plywood is covered with a linoleum type product.
Ever heard the term "Value engineer"?
He's the guy who comes around after the new product is found to be a success, cheapening it to squeeze more profit from it as now customers find the item they bought is not as good as a seemingly identicle item previously purchased.
I'm wondering if that report wasn't sponsored by the plywood council?
OSB circa 1979 versus modern CDX plywood proved the old OSB had no creep at all and the new plywood warped like hell. The planned obsolescence of lesser exterior grade glue has kicked in like Jim is suggesting. They make wood products to be expendable now. The only solution to fight them is to use higher quality paint to seal everything. Paint used to be better too.
The 1979 wood wasn't painted year after year either. Twice in it's whole 30 year life cycle, now a third time in the new milloonium. The original haunt was outdoors a lot of years with no roof. The new haunt seemed ruined out one year. It was certainly creepy.
After watching the tsunami videos I'm wondering if our newer haunts, made out of recycled wood products might make a geiger counter kick? Gonna have to come up with a lead additive for paint. Don't lick the walls kids.
OSB vs. Plywood
We use plywood extensively. I do have a small handful of OSB that I covered with vacuform or paneling.