You can’t keep wood from moving, but these 10 tips and strategies can help you avoid problems.
1. AVOID MITERS OUTDOORS
Miter joints hide end grain and look more refined. But the effect is ruined when the miters don’t meet tightly. Huge changes in humidity, and wetting and drying from rain and sun, cause wood to move more outdoors than it would indoors.
So whereas a miter joint will look good for decades indoors, it may start to look really bad after only one season outdoors. That’s why it’s usually better to avoid miters outdoors whenever possible. Use a butt joint instead.
2. PLAN FOR DECK BOARD MOVEMENT
Deck boards can shrink or expand after they’re installed, depending on how much moisture they contained when you fastened them down. To allow for this, space wet treated boards with a 16d nail (1/8 in.) and dry boards such as cedar decking with a carpenter’s pencil (5/16 in.).
3. ALLOW EXPANSION SPACE FOR WOOD FLOORS
If you’re installing an engineered wood floor, follow the instructions carefully—they include all the information you need about spacing. In general, floating wood floors that aren’t nailed or glued down require about a 1/2-in. space around the perimeter and enough clearance at thresholds, doorjambs and other obstructions to allow movement. Solid wood floors also require at least a 1/2 in.-wide expansion space around the perimeter.
4. LET TABLETOPS FLOAT
One of the most common errors that beginning woodworkers make is to securely fasten wood tabletops to the underlying frame.
Tabletops tend to be wide, and wood moves a lot across its width.
Restricting the movement with screws or nails can cause the top to crack as it shrinks. To avoid this, use special tabletop fasteners or some other method that holds the top down but still allows the top to expand and contract.
5. LET WOOD ACCLIMATE
Since the relative humidity of your indoor space may be quite different from the humidity where your trim or flooring was stored, you should always allow time for the material to acclimate.
The wider and thicker the trim or flooring boards are, the longer you should leave them in the space before installation. Thin, narrow trim may only take a day or two to reach equilibrium with the room’s relative humidity. Wide or thick boards should be left in the room for at least four days before you install them.
Of course the trim or flooring will still move a little after it’s installed, but at least most of the change will have occurred beforehand.