Your Guide to Mastering Wood Warpage

Wood warpage is a persistent challenge that many cabinetmakers will encounter.
Prevention is always preferred to correction, but understanding both approaches will save you valuable time, reduce project waste, and produce quality standards that lay the foundation for professional wood craftsmanship.

Understanding Wood Warpage

What is wood warpage? It’s a change in the shape of lumber that’s caused by uneven changes in the moisture content in different parts of the wood. Due to these uneven changes, the wood doesn’t maintain its equilibrium moisture content (EMC) uniformly across the different sections of a board. This ultimately creates internal stress that manifests as dimensional changes.

Primary Causes of Wood Warpage

The most common causes of warped wood are:

Moisture Imbalance. This occurs when one side of the wood absorbs more moisture than the other, which causes uneven expansion and contraction. The leading cause of this is due to not having a climate-controlled storage space, causing temperature levels and ultimately the humidity levels to significantly fluctuate.

Heat Exposure. Prolonged exposure to sunlight or heat can speed up moisture evaporation on the side that’s exposed to the heat. This uneven drying can create internal stress that will manifest as warpage.

Improper Storage. Storing wood in damp or humid conditions can lead to warping. Storing the wood upright or without proper support can cause stress and ultimately bending over time creating warpage. This is commonly seen in products that are larger in panel size.

Types of Wood Warpage

Understanding the different types of warpage can help you come up with a more effective correction strategy when needed:

Bow Warpage. This is a case where the board is curved lengthwise. It’s often caused when the top side of the board that’s laid on a flat surface dries faster than the bottom-facing side.

Cup Warpage. This type of warping happens across the width of the board, which forms a
concave or “U” shape from one end of the board to the other.

Twist Warpage. This is characterized by a twisted rotation of the wood plank somewhere along its length. A spiral or diagonal grain can often be the cause of twist warpage.

Crook Warpage. This warping is when a wood board is curved along the entire length of its edge.

Correction Methods & Prevention Strategies

When it comes to correcting wood warpage or preventing it from happening in the first place, there are a few different techniques to know of.

Correction methods for warped wood include:

Adjusting Moisture. Apply moisture to the concave side of the wood and allow it to dry evenly to help straighten it.

Weighting. Place weights on the warped wood to help it straighten over time.

Heat Treatment. Using a heat source like iron can help relax wood fibers and reduce warping.
To avoid damaging the lumber or creating new stress points, be sure to use controlled application of the heat.

To prevent warpage from occurring, follow these strategies:

Store Wood Properly. Store wood in a dry, well-ventilated area to help keep consistent moisture levels. Using stickers (thin strips of dry wood) between the boards can help promote air circulation. Lastly, maintain relative humidity between 30-50% with minimal fluctuations.

Acclimate Wood. Acclimatization involves leaving the wood for a period of time in the space where it will be installed. This can vary from a few days for thin, narrow boards to several days for thicker stock.

Manage Moisture. Use a moisture meter to regularly check the moisture content of your wood. To prevent warping, aim for a moisture level between 6% and 8%.

Seal the Wood. Sealing the ends of your wood can help prevent moisture from penetrating and causing uneven drying.

Want to Learn More?

Wood warpage can be a manageable challenge when it’s approached with the right prevention and correction strategies. If you’re curious about which wood species demonstrate the best (or worse) resistance to warpage, contact our team – we’re happy to share our insights!