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.

[Brad Shipton]

Rick Fisher owns several Canadian hardware stores and he commented about the typical purchasing practice of many hardware stores when it comes to sheet goods. It seemed to match what I see locally. Low quote gets the supply job. If they cannot tell you the source of the plywood I would be suspicious. That said, I know Home Depot carries Columbia Forest products and that is a quality product. The amount of stock they have of this seems to have dwindled over the years, so you will have to see what you have. My local store stocks none of it any longer, whereas years ago they had bundles of stock. They will gladly get me lifts and mark it up 50% over the cost of the wholesaler I go to. I suggest you find a wholesaler or a cabinet shop to buy from if you start buying a little more. The mark up at hardware stores on cabinet goods is quite high and you will find a greater number of finish grades at a wholesaler.

[Wayne Lomman]

From the other side of the world, the same problem and the same solutions. The cheap and cheerful shops buy ply from anywhere at a price, not a standard. You might be lucky but don't expect the odds to be in your favour. I find softwood ply from any supplier to be unreliable unless buying AA or AB.

As regards odors from ply, I find that south east Asian ply is very good but north east Asian ply, chip board and MDF to be almost impossible to work with to the point of guys off on compo with horrendous skin rashes. Cheers

[Ken Combs]

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

In my area all plywood is now undersized (metric, no fractional). But, MDF core is fractional. I like flat panel doors and use the MDF. And, my shaper and router cutters make a properly fitting panel recess, not slightly loose. Even better, there is no need to allow expansion space as it it very stable.

Not an overall solution to warped ply, but were MDF core would fit in your scheme of things, it is superior IMO.

[Wayne Lomman]

Now I have heard it all. The manufacturers calling mdf core products ply? I'm off to bed and tomorrow I will be working with timber that came from the tree to the sawmill to me. Cheers

[Peter Kelly]

That said, I know Home Depot carries Columbia Forest products and that is a quality product.It's also formaldehyde free.

[Curt Harms]

The manufacturers calling mdf core products ply?

It appears so though veneered sheet goods might be more appropriate.

VC=Veneer core, FC=Fiber core (likely MDF)? A sample:http://industrialplywood.com/images_common/ip_spacer.gif



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WHITE MAPLE–Select Plain Sliced


http://industrialplywood.com/images_common/ip_spacer.gif
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GRADE
CORE


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1/4"
4 x 8
—
A-4
VC (http://industrialplywood.com/13info_index.html)


http://industrialplywood.com/images_common/ip_spacer.gif


1/4"
4 x 8
Beaded 1-1/2" OC (http://industrialplywood.com/13info_index.html)
A-4
FC (http://industrialplywood.com/13info_index.html)


http://industrialplywood.com/images_common/ip_spacer.gif


1/4"
4 x 8
White Maple Bk.
A-1
FC (http://industrialplywood.com/13info_index.html)


http://industrialplywood.com/images_common/ip_spacer.gif


1/4"
4 x 10
White Maple Bk.
A-4
FC (http://industrialplywood.com/13info_index.html)


http://industrialplywood.com/images_common/ip_spacer.gif


3/8"
4 x 8
White Maple Bk.
A-1
FC (http://industrialplywood.com/13info_index.html)


http://industrialplywood.com/images_common/ip_spacer.gif


7/16"
4 x 8
White Maple Bk.
A-1
FC (http://industrialplywood.com/13info_index.html)


http://industrialplywood.com/images_common/ip_spacer.gif


4 x 10
White Maple Bk.
A-1
VC (http://industrialplywood.com/13info_index.html)


http://industrialplywood.com/images_common/ip_spacer.gif


1/2"
4 x 8
White Maple Bk.
A-1
VC

[Erik Loza]

There are large areas of the country where plywood is only available from the big box stores...

This ^^^... My dad lives in a pretty rural area of the Southern California desert. BORGs are the only source for plywood (or any kind of lumber) near him. Or, a full day's round trip. Those of us who have real wood suppliers nearby are pretty lucky.

Erik

[Martin Wasner]

No semi local cabinet shops? I wouldn't hesitate selling sheet stock to somebody that walked in, but I might be unique in that.


There's a hybrid out there, I can't remember what it's called. CFC perhaps? It's the face veneer, MDF, then a veneer core. The salesmen were pushing it pretty hard a few years ago. It's flatter which is nice, also a bit more consistent on thickness, but that's about it.

I haven't used a brand of plywood yet that didn't have some potato chips hiding in the unit. I currently use a Roseburg, white two faced Birch ply that I'm paying $69 a sheet for, most of the time it's pretty flat, but there's always a few in there that are cranky. Colombia is a nice plywood, but I kept rejecting it because I couldn't get it with decent enough faces no matter how I told any supplier what I wanted. White two face doesn't mean the backside can look like complete crap and full of brown streaks. So I keep going back to the Roseburg stuff. I wish I had the capital and space to order ten units of plywood to my specs and just have it pressed.

Thickness drives me more insane than anything though. Why can't they make it 3/4", or at least close(r)? I routinely get stuff that is dang near 11/16" in a unit. That raises heck with cumulative errors in boxwork. Especially when your hardware functions off of the carcass and not the face frame.

[Garth Almgren]

That said, I know Home Depot carries Columbia Forest products and that is a quality product.
It's also formaldehyde free.
That's PureBond plywood (http://purebondplywood.com/) you're talking about. I've always been reasonably impressed with the quality, considering that it comes from a BORG.

In my area, we have a wholesaler called Plywood Supply (http://www.plywoodsupply.com/) (have to be a contractor or a lumber yard to buy from them) or Midway Plywood (http://www.midwayplywood.com/) for retail. Plenty of choices, so my biggest problem is usually how to transport full sheets, and how to pay for them. :D

[Brian Tymchak]

I've struggled in the past with some of that China ply and started using the more expensive cabinet grade plywoods. But I've had decent results in the last few years with the Purebond Plywood at HD. It's a Columbia Forest product as Peter mentions. And IIRC, it measures very close to its dimension. IOW 3/4" is 3/4". Only the very occasional void and it is usually pretty small.

[Peter Kelly]

PureBond from HD should be identical in quality to what non-box store plywood vendors sell.

I'm sorely missing the Arauco material that Home Despot used to carry. Seems impossible to find now.

[Garth Almgren]

PureBond is a Columbia Forest product.

[lowell holmes]

In the Houston area, both Hardwood Lumber Co. and Clark's Hardwood Lumber have flat, full thickness cabinet grade plywood. It is beautiful to look at.
Back in the 80"s the chain lumber yards were selling 23/32" thick plywood, so cabinet hinges did not fit well. It aggravated me no end. I was glad to find full measure plywood.

[Peter Kuhlman]

It is so hard to find a quality supplier. I purchased 8 sheets of oak veneer plywood from Hardwood Lumber Co. and cut it up into the panel sizes I needed. Stacked it up carefully in my climate controlled shop and when I went back a couple days later to start assembly most of the pieces had started delaminating! I mean some entire pieces had separated. Supplier said it was not their problem as I must have done something wrong. Took me about a week to reglue and clamp all of it to get something I could use. Will never be going back to them.

[Brad Shipton]

To see why the thickness varies you should watch this video link (https://www.youtube.com/watch?v=LrCt5kJwcyw[/URL]). When you see how the log is unrolled to create the veneer leaves and consider that they only dry and grade the veneer sheets before glue up I can see how you end up with so many voids and thickness variations. What has changed in production since the plywood was thought to be more user friendly? Adhesives, and tree age. The process still seems to involve a lot of manual labor at the layup stage, so it does not seem they have changed much from the production side. I suppose the plywood suppliers are fighting the same problems we fight with when we are building with hardwoods.

[scott vroom]

What I read some time ago is that Asian (or any cheaply made plywood) warps because the veneers have different moisture content when glued together. The process of the veeners drying after glue up causes the warping/twisting. Quality plywood manufacturers use mechanical dryers to balance veener moisture content prior to glue up. Makes sense to me.

I use Columbia for most casework

[Robin Frierson]

Lowes carries Arauco ply here in NC and its not bad. Thats what I have been buying for shop stuff. I have to get my ply cut, cant handle full sheets anymore also no truck. So the big box stores cut it for free. I stand around waiting forever at the lumber yard. They dont really care about the hobby guy buying three sheets and wanting it cut.

Going to take a chance on some HD maple ply soon for cabinets at 50$ a sheet. I am sure it warp some when I cut into panels. I did get some 1/2 baltic brich in 5x5 sheets from Wall lumber for the drawer bottoms at 40$ a sheet.

[Carroll Courtney]

I remember going to the home center and picking afew sheets and it was perfect,core was poplar.But then it was made up in Temple Tx which now its made in china or who knows where:(

[Larry Frank]

Aruaco ply is the best I have found. In my area it is carried by Menards and they store it flat.

[mreza Salav]

Yes, buying from a good lumber source and buying NA product helps but even they will wrap if not stored properly.
Those with a combination of ply and mdf core (which are typically called combo-core here) are better in staying flat and have a more consistent thickness (but more heavy to work with). All plywood that I have seen (those manufactured here) are all metric. MDF/Melamine is still imperial (3/4" is 3/4").

[Mark Blatter]

Now I have heard it all. The manufacturers calling mdf core products ply? I'm off to bed and tomorrow I will be working with timber that came from the tree to the sawmill to me. Cheers


I have used a ply that has an mdf core, but it has wood ply on both sides. The advantage is that it stays flat, plus the veneers are thick. I swear they are 1/16" or better in thickness. It isn't just mdf with the veneer, but has several plies surrounding the mdf, then the outside vneer. I would use it any time in place of anything but BB.

[mreza Salav]

I have used a ply that has an mdf core, but it has wood ply on both sides. The advantage is that it stays flat, plus the veneers are thick. I swear they are 1/16" or better in thickness. It isn't just mdf with the veneer, but has several plies surrounding the mdf, then the outside vneer. I would use it any time in place of anything but BB.

Are you sure it is not ply in the core and MDF outside? The idea is MDF outside gives a smooth/flat surface under the veneer and the ply core is good for holding screws.

[Peter Kelly]

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.At least it wasn't a utility knife blade pressed in there. Don't ask me how I know...

[Bill Neely]

I drive an hour to Tree Products in Eugene for plywood, even their shop grade maple is good, I make cabinet boxes with it. Bonus that it's all within a few thousandths of 3/4". A lot of the stuff they sell, including the shop grade maple is made in Eugene by States Industries - the makers of Appleply.

*I worked in a plywood mill, here's a few facts: all the veneer is run through a dryer and graded as it comes out, the better stuff grades out for either faces, backs or centers, the lesser grades are cut to length for core (cross plies). Veneer lathes are very accurate and the knives are changed at least once a shift. Where I worked the spreader crew (the guys laying up the plywood) busheled, they got paid by the inch but they were experts at what they did, the mill didn't tolerate any overlaps or gaps. It was amazing to watch them work. When I worked in plywood the only thing that was laid up by machines was sheathing - CDX, I don't know if that's changed.

[Jim Becker]

A friend gifted me a sheet of cherry MFD core material a number of years ago. It was amazingly flat and the veneers were thick and beautifully figured. "Heavy", too, because of the nature of MDF. It was a true 3/4" thickness. I used it for the end panels of the three vanities I made for our addition in 2008. While I wouldn't use it where significant structural strength was needed, I wouldn't turn it way for most projects for sure if it fell into my lap. :)

[Randall J Cox]

Wow, think I hit a nerve with my warped plywood Q. Learned a lot from lots of experiences of you all, thanks. I did go through a plywood factory back when I was a teenager somewhere around Eureka, Ca (northern Ca) and it was really interesting. That was before all the "conservationists" shut all that stuff down with spotted owls, etc. Anyway, we do have a lumber co in town and I think I'll try them next. I do think that HD lumber and ply seems to be a cut above (pun intended) Lowes from my limited hobbyist experience... Randy