Warped boards and panels are considered by many do-it-yourselfers and even experienced carpenters to be useless. While the process of restoring these pieces of wood isn't something that everyone has time for, you shouldn't consider a warped board to be a lost cause. In fact, all you really have to do is wait for the right moment, and you can help the board straighten itself. Read on below to learn about a time honoured solution for all kinds of warped wood.
Store the warped wood in a dry, secure place until the next hot, sunny and clear day. Make sure that the wood is as dry as possible before putting it into storage. If there is any risk of moisture or leaking in the place where you store it, check on the wood during times of heavy rainfall or high humidity. Exposing the board to more moisture will just worsen the warp.
Water a section of lawn at least as big as the board or panel. Do this in midmorning of a hot and sunny day.
Lay the wood down on the watered lawn with the concave side facing down. The concave side is the side that is "caved" in. Severely warped boards may only touch the grass on the very ends when laid down this way.
Leave the wood out on the lawn all day. When the sun starts to set and the heat of the day has passed, bring the board into a garage or basement.
Dry off the wood with an old towel. The warping should either be completely corrected or improved. If it's still a little warped, repeat this procedure at the next opportunity. In either case, you should lay the board flat on a dry indoor floor for 24 hours. Lay out the board with the concave (or, hopefully, formerly concave) side down.
If your wood is small enough, you can do this in the winter by laying the board on its convex side over a radiator. Cover it with a damp towel or cloth first to give it the moisture it needs to straighten out.