Understanding Wood Movement: What You Need to Know

If you’ve ever tried to open a wooden door in the summer only to have it stick in the frame, then you’ve already encountered wood movement. In today’s blog, the lumber experts at AIFP offer some insight into what wood movement is and how to plan for it so that you’re next project isn’t ruined.

Understanding Wood Movement: The Basics

Did you know that fresh-cut lumber may contain more water than wood by weight? That’s why lumber needs to be dried before it can be put to use. During the drying process, lumber loses moisture and shrinks until it reaches a point of equilibrium with its environment. That said, even after it’s been dried, wood will continue to take on moisture and expand during the summer months when humidity is high and shrink in the winter months when the air dries out. This movement is seasonal and relatively gradual, which means you likely won’t notice daily or weekly changes, but you might start to notice sticking doors, large gaps, or cracks over time.

Can you Prevent Wood Movement?

No. Because wood is hygroscopic, it will always absorb water from its surrounding environment. That said, while you can’t prevent wood movement, you can manage it.

How to Manage Wood Movement

Choose Your Wood Species Wisely

Not all woods have the same degree of movement. In fact, the more stable the wood, the less movement you’ll see over time. Redwood, cedar, and fir tend to be the some of the most stable woods to use if you’re trying to manage wood movement.

Consider the Direction

Wood doesn’t just move in all directions equally. While the width of the board is often affected by wood movement, you should be less concerned with boards getting shorter or longer.

Pay Attention to the Grain

The grain orientation of a piece of wood has a big impact on how much it will move. That’s why you’ll want to consider the grain pattern when choosing wood. A flat-grain board, for example, will move about twice as much as vertical-grain board with the same change in moisture content. Int his case, the grain is determined by how the board was cut. Quarter-sawn wood, for example, will have vertical grains, while plain-sawn boards will have flat grains.

Let Wood Acclimate

Humidity can vary from climate to climate, but it can also vary from room to room. That’s why it’s important to store boards in the room they’ll be used before installation. If you’re working with narrow boards, it likely won’t take more than a day or two for them to reach their equilibrium, but if the boards are thick or wide, they’ll likely need at least four days to acclimate.

Finish Your Wood

Finishing your wood won’t entirely prevent wood movement, but it may slow the rate of expansion and contraction. Wood finishes can also absorb dirt and oils, which can keep your wood looking great for years to come.

Plan for Movement

One of the best things you can do to manage wood movement is to plan for it in the construction and design of your project. Not sure how to plan for wood movement? Start by leaving some extra space for expansion and contraction. If, for example, you’re working on a deck, leave some space between each board. If you’re installing a hard wood floor, don’t fill in the cracks. You can also use fasteners instead of screws or nails for certain applications, which can hold things down while still allowing them to expand and contract as needed.

Adjust the Humidity

While we can’t control the humidity outside, there are ways to keep the humidity relatively stable indoors. Consider using dehumidifiers in the summer and/or humidifiers in the winter to try to keep the humidity in your home as stable as possible.

Now that you have a better understanding of wood movement, it’s time to start your next project. Contact us today to learn how AIFP can help you meet your diverse construction, manufacturing, and industrial needs. In the meantime, check out our lumber blog, where we cover everything from pressure-treated wood to dimensional lumber.