With the changing of the seasons in our neck of the woods, the wood in our shop and homes are changing. This change is caused by the relative humidity and moisture content in the air. Typically, when there is more relative humidity (summer) the wood swells, and less relative humidity (winter), the wood shrinks. Does this mean that a shelf goes from being 12 inches long to 10 inches long in the winter? No! The measurement of the width of the board is what changes. For example, a 12 inch wide board can be closer to 11 7/8″ or 12 1/8″ depending on the time of year that it is being used. Generally, the softer woods like alder and pine tend to move more than the harder woods like hickory and maple.
So what does that mean for you and I? We have rustic maple flooring we used in our house. We bought the rough lumber, ripped it on our straightline rip saw to different widths, and ran it through our moulder with a tongue and groove pattern on the sides. When we installed it, we made sure to leave a gap on all the walls to ensure that there was enough room for the wood to shrink and swell with the seasons. If we hadn’t left a little space, there would be a chance of the wood popping up off the subfloor, or pushing the sheetrock in on the walls. We also left a small gap in the groove part of the tongue and groove pattern to allow for the movement of the wood on the joint.
Another part of our houses that needs that small gap is our kitchen cabinet doors. If you have raised panel doors on your cabinetry, your carpenter took into account for the shrinkage and swelling of the wood doors. There is a small gap on the inside of the styles and rails to allow the center panel’s movement which minimizes the movement of the overall door.
We are always after our children to shut the door! Our doors always shut better in the winter when the door jam is shrinking. That also causes a small problem when you might notice cold air seeping in on the bottom or sides of your doors. It’s not poor construction, just natural shrinking.
So next time you buy a 1 x 12 at your local hardware store, just remember it might not be as wide as you were planning or wider, depending on the season and how much relative humidity you have in your air!