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.
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Read the Inspection Quality Label
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Buy .40 for ground contact (deck posts, fence posts,
etc.) or above-ground use (deck framing, fencing,
etc.).
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Buy treated wood that contains a water repellent when
available. The water repellent helps stabilize treated wood and reduces
cracking and warping.
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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 (below).
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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.
