How Warping Impacts Wood Boards

While an Oregon State University professor for more than four decades, Doctor A. Morrie Craig conducted extensive toxicology research. Passionate about hiking and the outdoors, Dr. A. Morrie Craig also enjoys woodworking in his free time.

One of the challenges of wood over time is its tendency to warp. As a natural material, it is constantly equalizing to the level of humidity of the surrounding environment. Dry pieces can gain moisture through the surface pores in a humid environment, with the fibers swelling and the board slightly expanding. Conversely, wood will release moisture in a dry environment. These processes are particularly problematic with thinner pieces of wood that have less warping force resistance.

Kiln-dried wood involves drying the newly cut lumber within a controlled environment until it reaches the desired moisture content. This strengthens the board and makes it more stable but does not completely eliminate the moisture level changes experienced by any wood over time.

In preventing warping, stack boards with spacers that allow proper airflow around each piece. Alternatively, stack them so tight that there is no gap between them, and lay a piece of plywood at the top.

If wood does become warped, identify the cup (inside face), which tends to have drier, shrunken fibers. Wet that side as if applying a finish on wood and let the damp board sit overnight, wet face down. Wait a day, and repeat if this doesn’t resolve the issue.