How to Prevent Warping and Splitting of Fence Boards

Is the prospect of warping and splitting holding you back from installing a wooden fence? Wood is a naturally beautiful fencing material, but it's also susceptible to damage from moisture and weather elements. Planning the fence well and taking care of it can reduce the risks of warping and splitting to keep your wood fence looking like new for longer.

Wood absorbs and releases moisture based on the relative humidity around it. If the wood you use for your fence has a lot of moisture in it, the material can shrink and warp as it loses moisture or dries out. If the wood has low moisture content, it might soak up moisture from the air and swell. Creating a balance between the wood's moisture and the relative humidity in the air is referred to as equilibrium moisture content (EMC), and the adjustment process can vary in length depending on the wood size, grain, and coating.

Wood that you purchase as fencing material should have already reached EMC, but it still needs time to acclimate to your home's environment. Warping can often happen shortly after installing the fence if the wood used isn't cured or dried well.

Ongoing excess moisture can also cause warping or damage to a wood fence. For example, if your lawn sprinkler constantly hits one part of the fence when you run it, that area could rot or warp due to the increased moisture.

If you're building a new fence, the type of wood you choose can impact the likelihood of the fence boards warping. Cedar, redwood, and fir are species of wood that tend to have more stability and resist warping or cracking. Dense cedarwood resists cracking and moisture-related changes. Redwood benefits from having a relatively straight grain pattern and naturally repels moisture. Fir becomes very stable once it's fully seasoned, so it resists warping and shrinking.

Regardless of species, wood for fencing is less likely to warp if it has straight grain patterns. Wood that comes from the middle of a tree is also less likely to warp. Spending more on high-quality wood increases the chances of having a straight, sturdy fence that lasts.

The way you attach the fence pieces can impact splitting. Choosing thicker, higher-quality wood decreases the risk of splitting, but any wood can split if you use improper fasteners. Pointed nails in particular increase the chance of the wood splitting when you attach it to the fence.

Instead, use screws if possible. If you use nails, choose blunt nails instead of pointed nails to reduce splitting. Predrill holes for the fasteners no matter what you use. Avoid overdriving the fasteners, which can also cause the wood to split.

Sealing your wood fence helps slow down the aging process. It also helps the fence age more evenly. A water-repellent sealer with UV protection can shield your fence even more to help it last longer. You typically need to wait four to eight weeks after installing the fence to seal it. After the initial sealant application, you'll likely need to reapply sealer every two to three years.