Different Kinds of Treated Decking Boards

Pressure-Treated Boards

• Pressure-treated wood is wood treated with a preservative injected deep into the wood through pressure and vacuum cycles. A common preservative, Chromated Copper Arsenate, or CCA, is now unavailable for residential use because it contains arsenic. Two preservatives, Alkaline Copper Quarternary, or ACQ, and Copper Boron Azole, or CBA, have replaced CCA. Wood treated with ACQ has a green appearance, similar to wood treated with CCA, and performs in a similar fashion. CBA is a copper-based preservative that turns wood honey-brown. The wood weathers to gray with age.

Creosote

• Creosote is generally used to preserve posts or railroad ties, rather than decking wood, although wood treated with creosote can be used as a foundation for the deck. Wood treated with creosote is a dark brown to black, due to the tar in the creosote. This wood is difficult to paint, and may give off a strong odor initially. Fumes can seep into the soil, killing nearby plants. Use creosote-treated lumber to create a rustic look to decks, raised beds or retaining walls. Do not use new creosote-treated lumber near vegetable gardens or other plants.

Considerations

• Occasionally, an unscrupulous lumber company may sell wood dipped in a small amount of preservative to give it the appearance of treated wood. Buy lumber through a reputable seller and ask the dealer for assurance that the wood has been properly treated. Lumber may be stamped with the letters AWBP, which ensures that the manufacturers comply with recommendations from the American Wood Preserver's Bureau.

Ratings

• Treated wood is labeled to indicate the amount of preservatives injected in the wood per cubic foot. The higher the number, the more preservative the wood contains. When buying decking boards, choose lumber with a higher number, such as 60, for wood that sits in the ground as the permanent structure for the deck. Treated wood with lower numbers are suitable for the decking and rails.

Alternatives

• If the thought of toxic chemicals and preservatives makes you nervous, consider natural lumber alternatives. Redwood and cedar contain naturally occurring organic compounds that deter insects and minimize decay. Decks made from these woods gray over time and may cost more than treated wood. Both treated wood and rot-resistant woods require regular maintenance and sealing. Wood-plastic composites, or WPC, are made from wood flour and plastic. This lumber is very durable, but is quite expensive and more difficult to install.