OSB or plywood of the same thickness -- what is stronger?

amakarevic

i need to apply a small (0.5"x24"x24") reinforcement plate in an application where the rigidity of the plate is relevant (skylight shaft wall behind drywall onto which to lean ladder -- i don't want the ladder to bust through the drywall alone). i happen to have enough of both OSB and plywood in stock and was wondering which would be stronger and more durable.

i tend to thing plywood cause it looks more coherent as opposed to OSB which is little pieces of glued wood chips.

thanks

goosebarry

My vote is for OSB.
OSB is more consistent throughout its thickness. Plywood may have internal voids and soft spots. With my luck the ladder would hit the soft spot.

I would also recommend that you mount a board wrapped in carpet across the top of the ladder to distribute the load across the wall, not just the top of the two legs. You might need to add additional studs, again to insure the weight is distributed across two studs.

tony.g

The great 'OSB v plywood' debate rumbles on and on!.
My money would be marginally on the plywood, but it also depends on how well the board is fixed to the studs. Sure, ply can have some soft spots ocasionally, but OSB is not brilliant if the fixings are too near the edge, particularly with 1/2" thickness. Could some glue be applied before fixing? Either way,the lateral force on the board from the ladder won't be that much if the ladder is correctly angled and the OP should be OK with either.

mae-ling

When I took my carpentry courses many many moons ago and if memory serves correct, plywood is stronger then osb for that type of application. But not greatly so.
I vaguely remember that plywood is stronger laying down but OSB is stronger standing on edge? I think. Maybe

kwikfishron

For what you're doing either is fine.

I'd be making my decision based on what I have laying around close to the size I needed.

I certainly wouldn't cut into a full sheet of one if I had a partial sheet of the other.

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mae-ling

http://bct.eco.umass.edu/publication...d-and-plywood/

Interesting read

ratherbefishing

Just for fun, build a 1' square of 2x4s. Lay a 12"x12" piece of osb on the box and whack it right in the middle with your framing hammer. Repeat with the plywood. Or nail one of each to each side and test. Report back. I'm curious.

ddawg16

I don't need to do it to know the result....

Each material has it's use.....

OSB today is much better than it used to be....the glues are better so it does not suffer as bad from swelling at the edges as it used to.

When you look at the cost....OSB is cheaper.....and is perfect for shear walls.

But for sub floor and roof sheathing...I prefer plywood.

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sammyg

http://www.nachi.org/osb-plywood.htm

goosebarry

Wrong test for the OP application, unless OP is planning on throwing the ladder at the drywall.

I thought about the OP post and my endorsement for OSB, and realized I don't think I would have any scrape OSB lying around to use because I usually go for plywood.

21boat

Amakarevic. I'm a little worried here. Your building and wonder about a 1/2 ply strength with a 24" by 24" area 1/2" thick to lean a ladder against.....

Been looking at ply wood for 40 years never saw a "coherent" one.

Put it this way I've been pouring concrete walls for decades. We use the Dayton Superior system that is basic ply forming.

With 3/4 ply drilling 24" OC horizontally and 16"vertically for snap ties with 2by4 whalers horizontally stand ply up and pour a 12 thick in crete wall weighing 4,740 with each side wall effected by 2,370 Pounds in shear and you concerned about what Ply to use to lean a ladder against. .. It doesn't matter at all which ply you use to lean a ladder against at a 24 by 24 OC

tony.g

What's all this about?

21boat

An example of how much weight a vertical 3/4 ply can handle in Shear at 24 OC as opposed to a 1/2 ply to lean a ladder against.

So compare a 300 lb man on a ladder leaning on a 1/2 ply with what, a 50lb shear load of ladder and man as opposed to 2,370 pounds of concrete in shear..

tony.g

21boat - I may be missing something but I still don't see what concrete has to do with it.

echobravo

the weight of a man on a ladder vs the weight of a concrete wall against plywood