Board Fence and Wall Problems

Shrinking and Swelling

• Wood is made up of thousands of cellulose fibers running parallel down the length of the board. Each of these fibers acts as a tiny straw in the presence of moisture, sucking water into the wood and gradually releasing it when conditions are dry. High moisture content makes boards swell, and low moisture content makes them shrink, putting pressure on hardware and surrounding boards. Reduce shrinking and swelling by coating boards with paint or water-resistant sealant.

Warping

• A board that looks straight and square at the lumber yard may not stay that way once it's part of your fence or wall. Warping refers to a natural process in which lumber twists due to uneven fiber shrinkage inside the board. The forces that cause a board to warp are strong enough to pull nails out of posts. To reduce the impact of warping, choose boards with a fine, even grain and use screws for construction instead of nails. Replace badly warped boards promptly.

Cracking

• Repeated cycles of shrinking and swelling are hardest on the ends of a piece of lumber. Because the ends pick up and release moisture more quickly than the middle, they shrink and swell faster and to a greater degree than the rest of the board. This added strain eventually results in splitting when the wood fibers separate from each other. Splits often occur around nail or screw holes, damaging the structural integrity of your fence or wall. Minimize splitting by covering board ends thoroughly when painting or sealing.

Rotting

• Wood rots when conditions for fungal growth are optimal. The wood must be moist but not waterlogged, temperatures must be between about 40 and 105 degrees Fahrenheit and fungal spores must be present. Under these conditions, boards will rot unless they are treated with chemicals that kill the fungus. In applications where boards are touching the ground or exposed to a moist environment, choose treated lumber or heartwood from rot-resistant species like cedar or redwood to extend the life of the wood.