Warped plywood project

[ron hokenson]

I have been trying to upgrade my skills and am building a shop cabinet with 3 sections for drawers. Each section will have 9 drawers so there will be 2 pieces of plywood with back to back 1/4" dados that the bottom of the drawers will slide in . The problem I think is with my selection of material and possibly the humidity in my garage. I chose 3/4" birch plywood and find that even though flat to start with, once my dados are in and I have cut the plywood to size(approx 22"X32"), the plywood warps so much I think I will have problems with the drawers if I make all them the same size. I want them uniform. Not sure on the solution for this. The plywood has not been painted or sealed yet. I was going to put a sealer on after the base cabinet was built.

Would sealing the plywood before construction be a way to prevent the twist? If I sealed it before, the glue wouldn't work as well if at all.

Is there a better grade of plywood that won't warp as much? Oak or okoume ? I chose birch as it was the least expensive hardwood plywood.

Would I be better not using the heat and leave it cold all the time? I live on the coast so it is about 50 if I don't use heat. I don't want to leave heat on all the time but it is nice when I work out there. I do use a dehumidifier.

I appreciate the advice on this forum.

Thanks in advance, ron

[Rod Sheridan]

Ron, many people have experienced the same problems with lower end plywood.

Some of the plywood I've seen in some of the big box stores didn't have a Canadian grade marking so you may want to check to see if your plywood meets a standard.

There are lots of horror stories of people seeing the plywood de-laminate in the store, I saw some that would have made great hockey sticks, no bending required.

I only purchase plywood from my lumber dealer now, they sell good quality plywood with a good selection of veneers, and of course Baltic Birch as well.

I normally use Baltic Birch, which is a bit more expensive since it's shipped from Europe.

It all seems to be a question of getting what you pay for.

Take your stuff back to the store and talk to the manager........Maybe they'll let you upgrade to a better product.

Regards, Rod.

[Tony Bilello]

I dont understand how places like Home Depot even stay in business.
Their lumber quality is extremely low. They even have warped MDF.

[Lee Schierer]

I only purchase plywood from my lumber dealer now, they sell good quality plywood with a good selection of veneers, and of course Baltic Birch as well.

I just started doing the same on the project I am currently working on. I bought 2 sheets of 3/4" oak ply. Both sides are good, the sheets are 48-1/2" x 96-1/2 so you can actually get two pieces 24" wide from a sheet. It is flat. I paid about $8.00 per sheet more than HD wanted for one sided oak ply. Did I mention that it is flat and has stayed flat in my shop?

[David DeCristoforo]

You could have this problem even with the best quality plywood. with a carcass the size you are making, nothing to serve as a "stretcher" to keep the sides parallel and several grooves (dados) in the sides, deflection is almost assured. You might think about a different approach. Maybe you could dado the drawer sides instead of the carcass sides. The you can attach runners to the plywood to carry the drawers and have basically the same "design" but without having to dado the plywood at all.

[peter newton]

I dont understand how places like Home Depot even stay in business.
Their lumber quality is extremely low. They even have warped MDF.

Some of the big stores in uk stock warped plywood and MDF, so annoying, I think the folk doing the stacking do not have a clue.

[keith ouellette]

I agree with david. I think you are asking for trouble with the plan you set out. I have had the problem you describe with cabinet grade birch from hard wood supplier.

When you cut the dados in the plywood you are removing the very thing that makes plywood so strong, the adjoined layers. with cuts in so many places too many of the layers are not attached across the surface.

If you put runners on the drawers made of hard wood the runners could swell and stick.

I'm betting you wanted to do it that way to maximize the drawer width.

I made some utility drawers for a garage with plywood cases and put hard wood runners for the drawers to slide on top of. I also placed a cross member from one side of the box to the other, towards the front but a few inches back, and just above the drawer frame to keep the drawer from tipping out. I put a piece on the back of the drawer that would catch on the cross member so the drawer could only be pulled all the way out by lifting up on the front. It was the only way I could think of doing it at the time.

It worked good, not as good as a full extension slider though. But a lot cheaper and gave me the little bit of added width I wanted.