Selecting your wood will be one of the most important steps as you plan to build your project. Pressure treated wood will help you build a long lasting, attractive project, but it requires infusing chemical preservatives into the wood product. Until 2004, the majority of the wood used in outdoor residential settings was treated with the arsenic Chromated Copper Arsenate (CCA). CCA was used to protect wood from rotting caused by insects and microbial agents. The EPA later required the chemical to be phased out of all treated wood products by December 2003. The arsenic may be gone, but some replacement materials include heavy metals like Alkaline Copper Quat (ACQ), Micronized Copper Azole and Monoethanolamine (MEA), while others rely on energy-intensive thermal treatments. We’ve identified a few new products that you can use as an alternative to their toxic counterparts:
Osmose’s MicroPro
Osmose’s MicroPro pressure-treated wood products were created by a new technology that helps protect the wood from termites and fungal decay. MicroPro uses Micronized Copper Quaternary (MCQ) compounds that protect the wood. This treatment process releases 90% to 99% less copper into aquatic and terrestrial environments when compared to standard treated wood products. The very small amount released bonds readily to organic matter in the soil and becomes biologically inactive, thus effectively eliminating eco-toxic impacts. The Osmose MicroPro technology is the first treated wood process to be EPP (Environmentally Preferable Product) certified by Scientific Certification Systems based on a lifecycle assessment. MicroPro treated wood products can be found at Home Depot, Menards, 84 Lumber, Stock Building Supply and many local home improvement and construction stores.
Titan’s Accoya Wood
Created by Titan, Acetylation is a new treatment technology proven to toughen up wood fibers and protect woods from harsh outdoor conditions. The process uses a chemical that, in its diluted form, is basically household vinegar. Through extensive testing, Titan determined that the acetylation process took the free hydroxils from the wood, which readily bind with water, and changed them to something that insects and fungus can't recognize as food. That change also made the wood harder and stopped it from shrinking and swelling. Titan’s process is compatible with most wood species, but Titan dubs the finished product as 'accoya wood' and it is initially showing up as a Forest Stewardship Council (FSC) certified radiated pine variety. Titan is looking to bring Accoya to market through partnerships with manufacturers of outdoor lumber, decking, doors and windows.
BluWood - Gore-Tex for Wood
While BluWood is not a pressure treated lumber, it does offer mold, fungus and termite protection. The difference between blue wood and pressurized wood is that water is not added to the blue wood. The absence of water makes it lighter so it’s easier to transport and easier to handle. BluWood is a GreenSpec-listed product because it doesn't have active mildicides in the chemical. Its cost is about one and a half percent more than the total cost of building a home using traditional lumber. BluWood distributors can be found here.
Considerations
Any exposed wood, pressure treated or not, should be protected with a high quality water repellent finish, and it should be stained with water repellent to help reduce warping, checking and splitting. If you wish to apply a paint, stain, clear water repellent or other finish to your preservative-treated wood, we recommend following the manufacturer’s instructions and label of the finishing product.
Pressure-treated wood should not be burned under any circumstances. Other products that are on the do-not-burn list are plywood, particleboard, chipboard and painted or finished wood.
Always install pressure-treated deck flooring with the bark side up, because pressure-treated wood tends to cup as it dries. Cupping is the tendency for wood to bend along its width (away from the bark side). You can tell where the bark side is by looking at the end grain of the board.
Use only screws or nails that are galvanized and designed for pressure-treated wood. Any of the many styles of galvanized metal brackets and reinforcements commonly used in construction today can be used outside with pressure-treated wood.
And finally, do not allow any space between boards when laying a deck floor. Pressure treated wood shrinks, even if you coat it with a preservative!