Understanding Wood Movement—The Key to Protect Your Projects

What is the key to preventing most of the damage to wood projects?

Understanding wood movement. Wood takes on and gives off moisture as the humidity and temperature around it change, and it swells and shrinks as it does.

If you don’t understand and plan for wood movement, it can spoil your project with warping and cracking.

Whether you’re using wood for furniture, flooring, cabinetry, or some other application, you’ll want to understand wood movement so you can plan for it before it causes problems. The following sections will show you how:

• Types of wood movement
• Factors affecting wood movement
• Wood selection and preparation
• Design considerations for wood movement
• Wood finishing
• Wood maintenance
• Troubleshooting and repair

Let’s start by looking at the different ways wood can move.

Types of Wood Movement

Wood movement is caused mainly by changes in moisture content. As wood absorbs moisture, it swells, and as it releases moisture, it shrinks.

How much it moves depends on direction. Wood moves very little along its length. Most movement happens across the grain, and tangential movement (parallel to the growth rings) is about twice as great as radial movement (across the rings).¹ That’s why quartersawn lumber shrinks and swells less in width than plainsawn lumber.¹

Keeping these differences in mind throughout the woodworking process can help prevent moisture-related damage in the long run.

Factors Affecting Wood Movement

Wood moves toward its equilibrium moisture content (EMC), the moisture content at which it is neither gaining nor losing moisture in its surrounding environment. Until it reaches EMC, wood will continue to swell or shrink. Changes in temperature and humidity change the EMC, so they lead directly to changes in the wood’s moisture content and to wood movement.

To minimize movement after you complete a woodworking project, make sure the wood is acclimated to its environment beforehand.

The wood itself also plays a role. Some species move much more than others as their moisture content changes. Going from green to oven-dry, for example, true mahogany shrinks about 4.1% tangentially and teak about 5.8%, compared with 8.6% for northern red oak and 9.9% for sugar maple.¹

By taking these factors into account throughout the woodworking process, you can minimize moisture damage in the long term.

Wood Selection and Preparation

As you plan your project, whether you’re building furniture, installing a hardwood floor, or taking on outdoor construction, here are some ways to account for wood movement.

Select the Appropriate Wood Species

As mentioned above, some wood species are more stable and less prone to movement, which makes them better suited for projects where wood movement is a significant concern. For indoor projects like furniture making and hardwood flooring installation, choosing a stable species helps your work last.

Spend time researching the species you’re considering. One useful resource is the Wood Handbook published by the USDA Forest Service’s Forest Products Laboratory. Chapter 2 describes commercially important wood species, and Chapter 4 covers how moisture affects wood, including shrinkage values for many species.

Choose Kiln-Dried Lumber

Kiln-dried lumber is dried in a controlled environment to a target moisture content, which reduces later shrinkage and gives you a more stable product.

Keep in mind that a “KD” (kiln-dried) or “S-DRY” (surfaced dry) grade stamp on softwood lumber generally means a maximum moisture content of 19%, or 15% for lumber stamped KD 15.¹ That’s well above the moisture content recommended for interior woodwork and furniture, so check the wood yourself rather than relying on the stamp.

Opt for Quartersawn Wood

Because wood moves more in some directions than others, the way a board is cut matters. Quartersawn wood has its growth rings at 45 to 90 degrees to the board’s wide face. Compared with plainsawn lumber, it shrinks and swells less in width and cups, checks, and splits less.¹

Check Moisture Content

Guesswork is not enough when it comes to determining the moisture content of your wood. You’ll need a wood moisture meter to get accurate, reliable data.

Two types of meters are available for measuring moisture content in wood: a pin-type moisture meter or a pinless moisture meter. Both can provide accurate readings if you use a high-quality meter. A pinless meter is often preferable because it doesn’t leave pinholes in your wood, and pinless meters generally take readings faster than pin meters.

When should you measure moisture content?

Do it before you buy the wood and again before you begin your project.

Check that the reading is as close as possible to the EMC where the finished piece will be used. In most of the U.S., the Wood Handbook recommends an average moisture content of about 8% (6% to 10% for individual pieces) for interior woodwork, flooring, and furniture, and about 12% (9% to 14%) for exterior uses. The interior average is about 6% in the dry Southwest and about 11% in damp, warm coastal areas.¹

Use an EMC chart to find the average EMC for your area.

If the moisture content of your wood is far from the EMC, you may want to find other wood rather than spend time drying it.

But if the number is only a couple of points off, all it needs is time to acclimate.

Acclimate Your Wood

Letting wood acclimate to its final environment before use helps stabilize its moisture content and reduces the chance of movement-related problems.

Acclimation involves storing wood in the space where it will be used, with good air circulation and the temperature and humidity at normal living conditions.

Acclimation time varies with species, thickness, starting moisture content, and conditions, so don’t go by the calendar alone.

How can you know when your wood is ready?

Use your wood moisture meter to see whether the wood has reached the EMC.

Only then can you safely begin to work. And even then, you’ll want to keep wood movement in mind.

Design Considerations for Wood Movement

By managing moisture content before you begin your project, you’ve set yourself up to avoid most movement problems. But wood will still move as the seasons change, so plan for it during the woodworking process too.

When designing and building wood projects, allow for expansion and contraction by leaving enough space between components. This prevents undue stress on joints and fasteners, which could lead to warping or cracking.

And since wood expands and contracts mainly across the grain, try to align your components with similar grain directions. This helps prevent differential movement and reduces the risk of problems.

You can also accommodate movement with the type of joinery you use. Here are some examples:

• Floating panels: In cabinet doors or other panel assemblies, floating panels allow for wood movement without stressing the frame or causing cracks.
• Breadboard ends: These are used on tabletops and other large surfaces to help keep them flat. Attach them so the top can still move across its width, typically by gluing only at the center.
• Sliding dovetails: This type of joint allows for movement along the joint’s length.
• Tongue and groove joints: Commonly used in flooring and paneling, tongue and groove joints allow for expansion and contraction while keeping a tight, even appearance.

Let’s look now at some considerations for specific projects:

Flooring and Paneling

Account for expansion and contraction to prevent buckling or gaps. Follow the flooring manufacturer’s installation instructions, including expansion spacing and underlayment.

Furniture Construction

• Case goods: When building case goods like dressers and bookshelves, consider using frame-and-panel construction.
• Tables and chairs: Use appropriate joinery and allow for expansion and contraction in critical areas, such as where a solid-wood top attaches to its base.
• Beds: Use floating panels or slatted designs for headboards and footboards.

Outdoor Projects

• Decking and fencing: Choose wood species with decay resistance. Leave proper spacing between boards for expansion and contraction.
• Garden furniture: Use stable species, durable finishes, and joinery that allows for movement.
• Pergolas and gazebos: Build pergolas and gazebos with strong joinery and adequate spacing.

Once your structural components have been fitted and attached, here are some moisture-related points for finishing and maintenance.

Wood Finishing

Finishes such as varnish, lacquer, and paint slow down changes in the wood’s moisture content, but they can’t prevent them.¹ Even a well-finished piece will move as humidity changes, so it’s still important to keep indoor humidity at reasonable levels.

Your options for finishes include:

• Film-forming finishes: Varnishes, polyurethanes, and lacquers build a protective film on the surface. They come in both oil-based and water-based versions, and water-based finishes generally dry faster.
• Penetrating oil finishes: Natural oils like linseed or tung oil soak into the wood rather than forming a film, and they give a low-sheen, natural appearance.

Apply the same finish to all sides of a piece, including undersides and end grain, so moisture moves in and out as evenly as possible. Prepare the surface by sanding and cleaning it thoroughly, follow the manufacturer’s instructions, and allow the finish to dry and cure fully.

Wood Maintenance

To maintain the quality and longevity of your wood projects, follow these wood care practices:

• Surface protection: Use coasters, placemats, or other protective barriers to prevent direct contact between hot, cold, or wet items and the wood surface. This helps avoid moisture-related issues and other damage.
• Avoid direct sunlight: Light changes the color of wood over time, and direct sun can heat and dry one side of a piece faster than the other. Position your wood projects away from direct sunlight, or use blinds or curtains to reduce exposure.
• Address spills immediately: Wipe up spills promptly to keep moisture from penetrating the wood and causing warping or cracking.
• Use appropriate cleaning products: Choose mild, wood-safe cleaning solutions for your wood surfaces. Avoid harsh chemicals that may damage the wood or the finish.
• Regular inspections: Periodically check your wood projects for signs of damage or wear, such as loose joints, lifting veneers, or worn finishes. Address these issues promptly to maintain the integrity and appearance of your woodwork.

Troubleshooting and Repair

After all your hard work, what if you notice some warping or cracking in your woodworking project? The first step in solving the issue is to figure out its cause.

You’ll want to:

• Measure the moisture content of the affected wood with your moisture meter and compare it with unaffected areas.
• Investigate the surrounding environment for moisture sources, such as leaks or high humidity.
• Assess the impact of other environmental factors, such as sunlight exposure or temperature swings.

Whether the cause is moisture, design, or the environment, fix the underlying problem first. Depending on the damage, you may be able to repair the piece, or you may need to replace the affected parts or boards with properly dried wood.

Use this guide as your starting point. By accounting for moisture ahead of time, you’ll save yourself the time, money, and headache of fixing problems later on.

Measure moisture content with a quality moisture meter, and take these steps to keep your wood projects beautiful and durable.

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Ron Smith

As Sales Manager for Wagner Meters, Ron has more than 35 years of experience with instrumentation and measurement systems in different industries.  In previous positions, he has served as Regional Sales Manager, Product and Projects Manager, and Sales Manager for manufacturers involved in measurement instrumentation.

Last updated on October 8th, 2026