How to Check Lumber for Warping

Wood can be warped or distorted in several ways, some of the distortions can be worked with and others will leave the piece unusable. When shopping for lumber check each piece you purchase to be sure that it will end up being the quality you need. The thinner the piece, the more likely it will be to find distortions, 1 x 2's, 1 x 4's and 2 x 4's should be examined closely especially if they will be used in fencing or shelving.

Lay the board flat on the ground. The top and bottom lines should be parallel. If the board does lie flat but curves upward or downward anywhere along the length it has a spring distortion. If the distortion is near the end of the piece if may still be usable if a shorter section is needed. Otherwise pieces of wood with spring distortions will have gaps when placed side to side. This can be critical when placing fence boards or flooring.

While the piece is still lying flat, check to see if the entire bottom of the piece contacts the ground from one end to the other. A board that has a hump is considered to be bowed. Bowed boards may still be usable depending on the location of the bowing and what the wood is being used for. Thinner boards can be flattened out with pressure.

If the piece is curling upwards or downwards along the length the boards is cupped. It may look like it is trying to fold over on itself. Cupped wood is very difficult to salvage and most likely will not be useful. Twisted boards are ones that may have several distortions in them. When the piece is laid flat on the ground it may have a curve or hump and all four corners will not contact the ground at the same time. The piece may rock slightly when pressure is applied. Twisted wood can be used is the warping is not excessive.

Wood can continue to shrink and expand even after purchase as it absorbs and releases moisture. If you are building a fence or project that will be exposed to the elements always use wood rated for outdoor use. Sealing the wood when the project is complete will protect it from warping due to heat, cold and rain exposure.

Wood working projects all require different types of wood. The quality of the wood you use can be a significant factor in the end result of the project. Some projects, like furniture, might benefit from a less than perfect wood if you want to achieve a distressed look. Other projects, especially construction work, will need the best quality wood you can find.