Wood is one of the most economical and versatile construction materials used in the marine environment, and pressure-treated Southern Pine continues to be preferred for use in a long list of marine applications. Marine designers, contractors and specifiers favor treated wood because it is readily available, easily repairable, and extremely durable. When it comes to floating docks and piers, wood decks are lighter, requiring less flotation. Environmentally conscious marina developers also point to the fact that wood is renewable and requires much less energy to produce than steel, aluminum, or concrete.
To assure long-lasting service in demanding marine environments, pressure treatment with preservatives is the most effective method of protecting wood. Southern Pine is the most treatable of all softwood species. Its unique cellular structure permits deep, uniform penetration of preservatives.
For most marine construction, waterborne preservatives are preferred. These treatments are clean, colorless and odorless. Leading waterborne preservatives approved for outdoor applications in the market today include Alkaline Copper Quat (ACQ), Copper Azole (CA) and Chromated Copper Arsenate (CCA).
Recent labeling changes mandated by the Environmental Protection Agency have removed CCA as a preservative of lumber products intended for general consumer use. ACQ and CA are replacing CCA in the outdoor consumer market, generally for the preservation of common lumber of one- to two-inches in thickness or small sawn posts, usually less than 5x5". Sold under a variety of trade names, ACQ and CA contain no arsenical or chromium compounds and provide the same resistance to decay and termite attack.
CCA Treatment Still EPA Approved for Saltwater Use
While ACQ and CA are effective in ground contact or freshwater applications, CCA still has an important role to play in harsh marine environments where wood is either immersed in saltwater (including brackish) or exposed to saltwater splash. That is why the EPA continues to approve the use of CCA for marine construction, as specified in the American Wood Preserver's Association Use Category Standard UC5 and Commodity Standard C18. Properly specified and installed, CCA-treated Southern Pine rejects destructive marine fungi and borers - the chemical treatment makes the wood an undesirable food source for these organisms. See a list of products that may continue to be treated with CCA here.
Marine specifiers will continue to select CCA treatment for structural components exposed to saltwater, such as round piles, sawn timbers and heavy dimension lumber used for cross bracing, pile caps and stringers. But with broad introduction of "environmentally friendly" ACQ and CA into the market, there are now alternatives to CCA for surface decking, railing and other components not exposed to salt water. Specifiers may now select economical ACA- or CA-treated Southern Pine decking as the "environmentally friendly" choice over costly and nonrenewable petrochemical-based composites.
