Help!!! Warping Plywood

[SATEAR]

I have not had a chance to cut out my sides and my 1/2" plywood is setting in my garage and we have had a week of continuous rain and cool weather.
Both pieces of plywood are now warped and have a bow in them. What do I need to do to keep them straight?

Thanks

[Galen]

Bummer. Humidity will do that to plywood. Keeping it stored laying down on a flat surface helps. If you can let it dry out on a flat surface, like on the floor in your home, it may go back to flat. It may also help to put another piece of thicker plywood on top, say 1" and add some weight on top of that until it drys. Good luck. Maybe other folks have better ideas.

[Wolfgang92025]

Make sure not to lay it flat on a garage floor. It will pick up moisture out of the concrete.
When I have more than one sheet, I use spring clamps to hold the corners together with the bow (low spot) touching in the center.
I'm sure more will chime in......

Wolfgang

[prohandyman]

Sometimes just assembling the ply to a structure (i.e.Tear drop framing) will straighten the panels. But if the bow is in the door area it is mighty tough to get them straight. I have even had to purchase more wood for doors on occasion.
FYI - I sorted thru a whole stack of plywood a while back, and as I pulled some pieces out of the middle they immediately bowed with warp. That tells me they were warped before being stacked and shipped, and returned to the warp as I removed them. Even after being compressed in a stack for an extended time. Wood can be fickle!!

[48Rob]

That tells me they were warped before being stacked and shipped, and returned to the warp as I removed them. Even after being compressed in a stack for an extended time. Wood can be fickle!!

Plywood can also be "wet" in a stack.
Bring a few sheets home and stack them somewhere, the sheet(s) exposed to the air will curl...

Sometimes paying more for lumber from a place that understands wood, is worth the extra cost.

(Big box store do not...)

That said, as the others have mentioned, dry plywood can EASILY pick up moisture from the surface it is stored on.
Any time ONE side absorbs more moisture than the other, it will move.



Rob

[caseydog]

What kind of wood is it?

I have never had 1/2 pine plywood that din NOT warp. I used 3/4 Birch on my TD, and it even warped just a bit.

If the warp is slight, you can probably flatten it out when you clamp things up for your build. The structure will force it flat (or, at least flatter).

If the warp is severe, it's going to be hard to do anything with.

If nothing else, get the plywood off the floor, and maybe clamp it together with some straight, stiff pieces of lumber.

Something I learned the hard way was to wait to buy my plywood until I was ready to use it. Sounds like you are having that learning experience, too.


CD

[doug hodder]

A "green" sheet of big box ply left leaning against a wall in a garage will cup as it dries as well. They turn so much material that they aren't too particular on moisture content. If you have several sheets sticker them to get them up off the concrete and between the sheets for air movement. Like previously mentioned, you'd be better off to get the stuff from a quality hardwood or ply distributor over the big box stores. I'll use big box ply on the floor, but not elsewhere. Doug

As a side note...once you cut your doors, find a place to lay them flat, like under the bed or the couch. They're a bear to flatten out once they're cut and left uninstalled for any amount of time. Just my experience.

[halfdome, Danny]

The proper way to store any wood sheet goods is laying flat in a rack with a sacrificial top & bottom piece to absorb any moisture. Even a unit (40 sheets) of particle board laying on the floor with stickers will not warp if there is a sacrificial sheet on top. We did this year after year one block from the ocean in Solana Beach California and we never had a warp-age problem. If your sheet is warped it will stay that way. Only attaching it to something structural will make it appear not warped. Like Doug said, store your doors flat. Also away from moisture. I spring clamp mine face to face with the lacquered insides out. Danny

[wannabefree]

My $.02 - plywood is cheap, time is scarce. Don't mess with this stuff. Buy new, and if it won't stay flat, buy new again. Don't trust that stuff from the big box for anything you care about.

Just my thoughts.

[aggie79]

My $.02 - plywood is cheap, time is scarce. Don't mess with this stuff. Buy new, and if it won't stay flat, buy new again. Don't trust that stuff from the big box for anything you care about.

Just my thoughts.

I agree - quality plywood is the way to go. Warped plywood isn't worth the effort. Although I usually buy baltic birch or cabinet grade plywood, I have had good luck with Arauco plywood from the BORG. There is a little premium for this, but it is much better quality.

I store my plywood on a rack and haven't had too many problems with warping. (the 3mm - 1/8" baltic birch will curl sometimes.)

[dan galvin]

Take it back and get new {the day you are ready to cut the sides and mount them] I hate cheep ply wood it happened to me too
and we will not be the last
Dan