Why is all plywood warped?????

[Randall J Cox]

Seems like no matter what thickness I buy, nor where I buy it, every piece off the stack is warped. If cut into small enough pieces, not an issue, but it sure is for larger pieces... Is there any known method to "unwarp" a 4x8 sheet? i wouldn't think so but, this is a talented group and I have learned a lot here. My main source is Lowes and Home Depot. I'm just a hobbyist but would still like to deal with flat plywood. What do cabinet shops do? Anybody have any ideas? Randy

[Todd Burch]

I buy plywood all the time that is not warped. I see your problem… you are buying it at a home center.

Find a REAL supplier of fine cabinetry plywood in your area. It's worth the extra money.

[Andy Giddings]

Randy, Todd's advice is spot on - if you ask the forum for a good supplier in your area, chances are they will point you to a supplier that has better quality. I believe MDF core Ply is less prone to warp but have never used it. Baltic Birch is nearly always flat but has a less than interesting appearance for furniture

[glenn bradley]

Nothing to add. If you want a quality product go to a quality provider. I have ply that has been stored vertically for nearly a year without issue.

[Ben Rivel]

Yep, as everyone else around here will tell you buying from the big box stores is your problem. You have to find a real lumber store/supplier. You should add your location to your profile so we know where you are and perhaps someone near you can recommend a supplier.

[Larry Frank]

I find that places that store the plywood on racks with arms have warped ply.

The Menards in my area stores it flat and is not warped.

[Chris Padilla]

On the other hand, I've had good luck buying 3/4" maple ply at HD. At $50/sheet, I've been very happy with it.

[Jim Dwight]

I also buy plywood often at big box stores and sometimes at hardwood plywood dealers. If I buy inexpensive subfloor grade plywood it pretty much always warps, even if it is flat when I buy it. But I've built a bunch of shop stuff from pine plywood from HD made in Chile that is only $30/sheet. Face veneer varies a bit but one face I would grade consistent as A grade and the back varies from about B to C. Nice stuff for the price and stays pretty flat. But it is interior glue. But I like to put a coat or two of finish on shop projects so it works.

I also prefer poplar for interior plys but rarely find it. Softwood plys tend to be less stable with more voids. More plys tend to be more stable. Baltic Birch is very nice plywood that is all birch - a better wood than poplar both in strength and consistency. But it is also relatively pricey.

Another difference between big box store plywood and nicer stuff from a dealer is the face veneer. I've only seen rotary cut veneer in big box stores. That is not terrible but doesn't really look like boards. You can get cut veneer that does look like boards but you pay more and it isn't available around the corner at HD or Lowes.

I think the trick is getting plywood that is good enough for what you are doing without spending more than necessary. That is sometimes available at the home center and sometimes not. I also find that warped plywood is still usable, just like warped boards, but it is more trouble. When you fasten it into your project it should pull the warp out.

[Jim Becker]

I buy mine from Industrial Plywood...not only is it flat, but if I get something that's not right, they will pick it up and drop off a replacement next time they are delivering in my area. (about twice a week) I've only had to complain once...

I'm not a cabinet shop, but these folks deliver to some local cabinet makers I know, too. There are several other similar suppliers, although they cater to "trade only". No cabinet shop would source material from the home centers.

[Andrew J. Coholic]

... What do cabinet shops do? Anybody have any ideas? Randy

Cabinet shops like ours, buy sheet stock in full lifts. We get it in, fork lift it into the storage part of the shop and it stays flat on the shop floor (off the concrete on 4x4's). Because it is sitting flat with a cover sheet on it, it stays flat until we start using it. I think changes in MC% make ply move just like solid wood. And when it is standing up not 100% vertical the weight also causes it to develop a "wow".

I find when you try and stand it up in racks, etc it starts to move. Left in the lift, as is, stays flat (not to mention scratch free and clean as well.

Sorry I dont know what to tell you. But I dont think it can be "straightened".

Also, we buy good quality, NA made panels. Most of it actually pressed up here in Canada. Generally a really good product. No Asian made plywood will see my shop. Everything off shore, thatI have seen is pretty low grade. Except for the Baltic birch, which we use a fair bit of. I know it also stays much flatter if I leave it as I get it in a lift, VS putting it in the racks (which I do for that stuff just to save floor space and because it gets cut up into smaller pcs relatively speaking).

[paul cottingham]

Because my daughter is sensitive to the adhesives used in the cheap plywoods, and because I believe in supporting local, I only buy NA (Canadian or American) ply anyways. And NA plywood made with soy glue to boot. So it works out that on the few occasions I have used plywood, the NA stuff has been expensive, but solid, stiff, easy to work with, and definitely not warped.

[Warren Lake]

spoke to a guy who was partners in a large lumber company close by. Told me they bought a lift from China to see. Said it stunk so bad they had to leave it outside. One day for curiosity they cut into it, told me they found an underwear band inside.

Now this would be going back a bit ill make a guess 5years since he told me. When I met him he owned a trailer bus including the building year later he moved and the building was for sale for over 2 million. Also hear he was a third partner bought into another quality plywood company, clearly a together guy. Only bought china once 1/8" oak because no one had anything else short of having it laid up. It was unbalanced but worked fine for that job.

[Greg R Bradley]

Anything in Home Depot or Lowes that claims to be plywood has only a vague resemblance to plywood.

[Curt Harms]

I too have bought some plain sliced red oak ply from Industrial Plywood. I didn't even know there was plywood that was not rotary cut until I browsed their web site. No voids, stays straight & flat and what I bought was 49" X 97" so there could be a few saw kerfs removed and still get 4' X 8' worth of material. More $ but worth it in many cases. Some things not typically found in Home Centers:

http://industrialplywood.com/04prod_cab_index.html

[Lee Schierer]

There are large areas of the country where plywood is only available from the big box stores. The plywood from big box places can vary widely in quality. One thing that I have learned is that plywood is like any other piece of wood regarding moisture content. If you expose one side to the air and the other is not, it will warp and curl. I never buy the top sheet or two. I get one from down in the stack and make sure when I get it home that it gets air circulation equally on both sides. As a result I've had very few issues.