How long should air-dried lumber sit?

I recently purchased roughsawn lumber that was air-dried for a year. How long should it acclimate in my shop before I can use it?
—George Poljak, Port Vue, Pennsylvania

The short answer, George, is that you should stack and sticker the lumber for at least a week in a controlled-temperature room if the lumber is 1" or less in thickness. If thicker, it most likely needs more outdoor air-drying.

The best way to put your mind at ease is to rely on a moisture meter. These devices cost between $35 and $285, and instantly show you the moisture content of lumber as a percentage, comparing the weight of water in a piece of wood to the weight of that wood when completely dry. Air-dried wood in your part of the country usually settles at 12–15%, which is satisfactory for outdoor projects. Ideally, hardwoods should dry to 9% or less for interior projects.

If a week in your shop doesn't get the lumber to that level, help the process along with a low-tech drying setup. Stack and sticker the lumber on a sheet of plastic, the bottom layer of lumber a few inches off the floor. Set a dehumidifier and fan on the plastic beside the stack, and cover the whole arrangement with more plastic. Regularly check the moisture content with a meter. When it reaches the target level, turn off the dehumidifier. Keep the fan running for two more days to let the entire stack stabilize at that moisture content.