Ask WWGOA: How to Flatten Warped Plywood

ask WWGOA text with a man posing


How can I flatten plywood? I am making some panels out of 1/2″ oak plywood. The panels are not completely flat and will not fit the grooves in the frame.

Submitted by Mackym


This may not be a fixable problem, but you can try. One downside to plywood is its tendency to cup. In the future you may want to try oak mdf (medium density fiberboard) instead of plywood. It’s much more likely to stay flat.

Using a sponge that’s slightly damp, moisten the concave side of each piece. Give the plywood some time and see if it flattens itself. There are lots of ‘it depends’, regarding how wet the sponge should be and how long the plywood has to sit, so you’ll have to experiment. A guitar I made had a plywood soundboard that was bowed. I used this trick to flatten it, but got it too wet the first time and it bowed it in the opposite direction. I then had to do the same trick on the other face.

Let us know how it goes for you.


Do you have a question for WWGOA? Ask us on Facebook or email Note: questions may be edited for clarity and relevance.

Share tips, start a discussion or ask one of our experts or other students a question.

Make a comment:
characters remaining

3 Responses to “Ask WWGOA: How to Flatten Warped Plywood”

  1. JIM

    George, You are going to laugh at my picture if I can upload it. In 1976, I found this device in the basement of a home that my wife and I just bought. I was never sure what it was but I have enjoyed woodworking ever since and have used it as a "hold down" vise on my workbench. I was watching one of your instructional videos the other day and something caught my eye. "Wait " - I said. That device that George used to secure a piece of wood onto the the surface of the workbench looked familiar. Sure enough, it is the same device that I have been using as a hold down clamp. Can you please give me some advice or "watch-outs" for mounting onto the side of my workbench. I am right handed. Do I need to mount it on the right side of my bench? Are there any "gotcha's" that I need to worry about when mounting it? Wish I could upload my picture??

  2. Sherry Bernard

    I have had success using the sun. Lay the plywood on the ground with the convex side up and within a sunny day or two, you should be back in business.

  3. Gary Coyne

    I had a piece of 1/2" ply warp really really badly and didn't know what to do with it. Then I figured it out: I had made some drawers for some shop storage, and cut the piece to be the drawer bottoms. I then cut into the convex side about 9/32" about every 1/2" apart. [After doing the middle, I'd cut one to the side, rotated the piece 180° then cut the other, reset the fence another 1/2" and repeat. This let me "flatten" the board and use it as the bottom of the drawers and it has worked quite well. Since it had already been bought, I couldn't bare to toss it. ;>)