Carpentry and Woodworking - Correcting warped plywood

I recently made a door out of plywood. The stiles are 4 inches wide and consist of 3 layers of 1/2 plywood to make the door 1.5" thick.

After I glued and nailed them together - and formed the door - I see that it is warped.

One one side Im not concerned because there will be three hinges that will keep it straight. But the other side has no support.

Im thinking that if i cut 3/4 off of the end, clamp the door flat, and glue a 3/4 piece of solid stock (1.5 inches wide) to replace the 3/4 i removed, that it would keep the stile straight.

Now, when I take a piece of 3/4x1.5x80 (length of the door), I can put pressure on it and bend it. Obviously that is due to its length. If I take piece that is 3/4x1.5x36 it doesnt budge.

Im assuming that when the piece is glued to the door that it is stronger - more like the 36 inch piece, and less like the 80 inch piece because it is supported all the way across.

In other words, if i used multiple pieces of 36" end to end, even if the door wanted to warp, it wouldnt along the 36" pieces - it might at the seams.

Plywood is not the material to make a door from. The edges aren't made to take the stress of the hinge screws. They will pull out. Making a door requires the rails and stiles to be made of solid lumber. You can inlet the plywood panel into the rails and stiles. I am having to do this on a renovation project I am on now involving a log cabin built in 1850. No one seems to have any doors that will look retro enough, so I make them. Rustic, but they work, and that is what the customer wants.

I imagine that you recall the original thread where the entire topic of building these doors was conceived. In the opening paragraph of that post, and also in my 2nd post in that thread, I mentioned that plywood will warp, and that you would have difficulty with the hinges pulling out (I believe I suggested predrilling and longer than usual screws). I don't blame you for wanting to try it anyway, since these doors have only cost you one sheet of plywood and the time you have spent on it. You might have figured it was worth a shot.

Two 40" pieces of 1x2 glued to the sides of the doors will not be stronger than one 80" piece of 1x2. Your 1/8" steel idea would work better, but again, you would have to predrill any holes in the plywood and use longer than normal screws.

I guess I should have gone for the solid wood. Plus I would have also justified getting a new router bit if needed.

Anyway, I figured that for any scerws going into the end grain, I would use cross dowels. Not on all screws, but maybe one on each hinge. And maybe with the steel as well.

A few more holes to repair, unfortunately. If I had taken the warping more seriously I would have gone for the solid wood from the start. But I cant see scrapping the project now.

So, now I just want to figure out the way that will be the least amount of work. Even the cross dowels force me to drill holes and plug them.

Could I take my new 1x2, rabbit out 3/4 in the center, by 1/8 deep and set the steel in that. Then, just glue the reinforced 1x2 to the door? This way, Im not Screwing the steel to the door - with cross dowels, and then capping with the 1x2. The steel would be, technically, floating inside.

I was even thinking of ripping the door on my table saw, about 1 inch from the end. The saw blade about 7/8 high. Then set the steel in the groove with liquid nails.

Any thoughts on redeeming the project and still saving $$$, and not going overboard with work/time?