Pressure treated lumber is a type of wood which is specifically engineered to be used on projects which are exposed to the weather such as decks and flower boxes. Pressure treated wood begins with a softwood such as pine or hemlock. A sealant formula is applied under pressure on the surface so that it seeps deep down into the wood's core.

The formula helped protect the wood from moisture, but in the early part of the 20^th century it was quite toxic for those who worked with it and even animals that were exposed to the final product. Arsenic was the base of the first formulas used to make pressure treated wood. Dogs and cats who've chewed on it experienced arsenic poisoning. Modern pressure treated wood of the 21st century uses Alkaline Copper Quartenary (ACQ) lumber. Although it has its some issues, it doesn’t have issues with toxicity.

When buying pressure treated wood, don't be surprised if the lumber at your your local home center is almost always dripping wet. The process of making it causes this phenomena although the outer edges are a bit dryer and tend slightly to warp outward. Because the lumber that has warped doesn't sell well, all manufacturers will get the wood to their distributors as fast as possible so that it sells before it completely dries unevenly.

When the wood is still wet, it's like a sponge and soaks up as much liquid as it possibly can. As the wood dries it shrinks somewhat. When buying pressure treated wood, inspect the long edges and look for blemishes and other weak spots. In addition, check the end grains and look for those which cross the board's narrow span because they're less likely to warp.

When building an outdoor project have each of the boards butt against each other as tightly as possible. As the wood dries and begins to shrink, you'll notice small gaps between the boards. To resist cupping, position any of the boards with their end grains in the shape of an arc so that the center of the arc of the board's end grain point upward. When trying to minimize the bowing, be sure you get to put at least one deck screw through the center of the board.

When working with pressure treated wood, use common sense safety rules. Use a quality dust mask as you cut the lumber as the sawdust will irritate your lungs. Always have good ventilation and do all of the cutting outside your wood shop. Good ventilation and the breeze helps disperse airborne sawdust.

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