Green alternatives to CAA-treated wood
Direct substitutes for CCA-treated wood include less toxic products such as ACQ (ammoniacal copper quaternary) and CBA (copper boron azole). ACQ is corrosive to standard steel over time—so stainless steel screws and nails and double-coated, hot-dipped galvanized hangers and hardware are typically recommended. CBA is less corrosive to steel. Aluminum hardware shouldn’t be used with either.
Both ACQ and CBA rely on copper as the active ingredient, and copper is highly toxic to many aquatic organisms. For this reason, neither should be used on boardwalks, docks, or decks overhanging ponds, marshes, or other aquatic locations. Neither ACQ nor CBA are approved for saltwater applications. For wood that isn’t exposed to weather, borate-based preservatives (without copper) are effective against insects while being much less toxic than other chemicals. Treatments using sodium silicate followed by heat offer a very attractive alternative to conventional copper-based treatments.
A responsible approach to rot-resistant wood
There are also problems associated with using naturally rot-resistant wood species, such as redwood and cedar. Clear-heart redwood is generally cut from old-growth forests. Redwood trees take a long time to mature, and there are very few remaining stands of privately owned redwood. Small but increasing amounts of redwood and cedar are available from certified, well-managed forests. The quick-growing second-growth redwood and cedar, with wide growth rings, is less resistant to rot and insects than old-growth wood.
Sustainably harvested, long-lasting exotic hardwoods such as Ipé, imported from Brazil and Bolivia, are increasingly available; look for Forest Stewardship Council (FSC) certification. FSC certification involves third-party evaluation and monitoring of sustainable forestry practices—and chain-of-custody verification that wood products were derived from certified forests.
Alternatives to wood decking
In some settings, a patio made from local stone makes an attractive alternative to a wood deck.
For exposed applications, recycled plastic lumber is an excellent alternative that will handily outlast most wooden decking materials: 50-year warranties aren’t uncommon. Products combining recycled plastic with wood fiber offer a more wood-like feel and less thermal expansion in the sun.
BIBLIOGRAPHY ITEMS
Building with Vision
: Optimizing and Finding Alternatives to Wood
by Dan Imhoff
(2001)