2 layers of 1/2 inch plywood vs 3/4 osb for woodshop floor

[cody michael]

I posted in another thread about redoing my woodshop floor. on craigslist there is someone selling pallets of 1/2 plywood for about 1$ a sheet, for half sheets, if I doubled these up, possibly use glue in between would it be stronger then 3/4 plywood? they are odd sized a little, 47 x 39, 50 x 38, 51 x 37 (APPROX 50 SHEETS PER PALLET mixed ) 1/2" thick $50 per pallet. but if 2 sheets equal 1 osb sheet, even double thickness that is 4$ a sheet, where osb is 12-13$ a sheet. any reason not to look into this?

[Charles Lent]

I would never use OSB as the exposed surface of a floor, not even in a workshop. I've seen where others have done this in their shops and later had problems with large pieces (layers of the OSB) lifting over time. If you can make the plywood dimensions work for you, that would be a great price for that much plywood. You might also consider using 3/4 OSB as the sub floor and 1/2" plywood as the surface floor. Gluing the two layers together would be a good idea. The two glued together layers of plywood would work too, but the available sizes might create a lot of waste when trying to put the seams over supporting structure. Using plywood for only the surface layer would allow much less waste because the seams could be anywhere. What is the plywood grade? This should also have a significant bearing on your decision. A very rough surface or large internal voids
will cause later failures when used in surface flooring.

Charley

[Chris Padilla]

It'll be some work and you'll need a gallon or two of glue, but it seems like a good deal IF the plywood is good. See if you can get a pic of the stamp on the plywood. I wouldn't use anything lower than a C face grade and exposure1 rating might be nice but not a deal breaker. You'll want to laminate these together with FULL SPREADS of glue (rolled on or spread with a drywall knife...no blobs and no 'S' pours). You might even be able to get clever and create half-lap joints after you laminate two sheets together.

[cody michael]

IIt's plywood from industrial packaging,nice have a bunch of titebond I and II. Would that be a workable glue choice? I got it on clearance probably can't use it before it goes bad.

[Chris Padilla]

I's open time is pretty short...get a helper to slop it on before it skins over on you. II will give you a bit more time. Either one is great...just move it when you start pouring/spreading. :)

[Larry Edgerton]

I would never use OSB as the exposed surface of a floor, not even in a workshop. .
Charley

Advantec......... Better than plywood. There are other brands of premium OSB as well, not the same animal.

[Jim Dwight]

I had 1/2 plywood floor in an attic room I finished. I added 7/16 waferboard over it and then 3/4 pre-finished hardwood over that. I did not glue them together but did overlap the seams at least one joist. The subfloor is very solid and the hardwood went down well. Two layers of 1/2 plywood should be even better as long as the plywood is good.

[Jim Andrew]

Odd sizes of sheets will be a pain. It would be easy if it were all 4' wide, but otherwise you will probably have to rip it all one width, at least the same for each strip across the floor. I would prefer 2 layers of 1/2" to one layer of 3/4, that construction was common 50 years ago. As far as glue, use construction adhesive.