From About This Project
Pressure-treated wood has a proven track record for durability in every part of the country. It combines the ease of working with wood with long-term resistance to rot and insects. Still, carpenters tell us, you’ll get even better results if you follow these selection, safety and technique guidelines.
Read the Inspection Quality Label
- Buy .40 for ground contact (deck posts, fence posts, etc.) or above-ground use (deck framing, fencing, etc.).
- Buy treated wood that contains a water repellent when available. The water repellent helps stabilize treated wood and reduces cracking and warping.
- Buy .60 for foundations or other in-ground use. Usually
you have to special-order this higher level of treatment through lumberyards or
home centers.
NOTE: The wood preservative industry has phased out the use of CCA (which contains arsenic) for most residential applications and substitute other preservative chemicals.ACQ (Alkaline Copper Quat) has replaced it.
Apply water repellent immediately after installing decking, fencing or treated wood railings to slow the drying process and reduce shrinkage. Many species that receive treatment are prone to twist, cup, crack and warp as they dry out. A water repellent (or oil-based stain) keeps them more stable. Expect to reapply the repellents every year or two.
Avoid treated boards with more than about 20 percent heartwood, especially if they’ll be in contact with the ground. The heartwood is the core of the tree. It usually doesn’t absorb the treatment chemicals as well as the outer layers of wood (sapwood) and is vulnerable to rot. When you use boards with a high percentage of heartwood, install them where they’ll readily dry out after rainfall. And be sure to treat cut ends.
Wear a dust mask, goggles and gloves when you cut treated wood. The chemicals in treated wood are toxic to insects and fungus and they’re toxic to you, too. While they won’t leach out of the wood, avoid breathing the sawdust and keep it out of your eyes. Don’t burn scraps, because the ash will contain a high concentration of the chemicals. Dispose of scraps in your ordinary garbage collection.
Soak freshly cut ends in a wood preservative (available at home centers and lumberyards for $10 to $15 per gallon). Cutting the ends often exposes areas that the treatment didn’t reach, especially in posts and timbers. Let them sit in the bucket for five minutes.