Oriented Strand Board (OSB) Warping

Warping usually implies the absorption of moisture, or a difference in temperature between one surface of the board and the other.

If the wall is warmer than the room, the sheets would bow inward at the corners, toward the room. Cold wall, warm room, bow toward the wall.

Same with moisture. Wet side will expand.

Or not.

When properly fastened to studs and joists, I've never had any warping problems with OSB.

From your description it seems that the finished panel warped after installation. Moisture condensing on the rear of the panels could cause them to swell and the edges to cup inward. How are these panels fastened to the walls? Was there a vapor barrier behind these panels?

I suggest a read here for some general information regarding plywood verses OSB (their similarities and differences).

http://bct.eco.umass.edu/publications/by-title/choosing-between-oriented-strandboard-and-plywood/

It might help you debug your current problem. Good luck!

I have a few sheets leaning against the shed that will be good for troughs soon, but if I screw to studs no more than 32" apart no warp occurs even if they get wet some

Question has the OSB warped or the covering of foam and/or vinyl shrank drawing it in on that side?

When laminating boards of any significant size, we always put what we call a balancer sheet on the reverse.. this can be a very thin melamine or a thicker plain laminate. We have found over the years that the application of a small cost increase prevents a large cost(replacement) in the future. This is from the shop-store fitting side but I think it will apply to you.. Hope it helps

I tend to agree with merc. If vinyl is applied to only one side this would cause an imbalance and could be the problem.

I have had osb bow but not to an extent that You seem to have. I use it mostly for siding and roofing so nailing or screwing 16 inch oc presents no problem.

oilcan13

Thank you all for your input!! I'm sure that the cause of the warping is due, in part, to the installer attaching it in only one spot (the center) at the bottom. I removed one of the pads to check for mold or moisture and found neither. I'm wondering if it could be possible that, due to the outside west wall (in North/Central MI) and the heated wrestling room there is enough condensation that the OSB is obsorbing all of the moisture, keeping the walls and pads from molding...

Thanks again, everyone!!!

Darvin