Guide to Sustainable Decking Materials
Finding truly sustainable decking materials can be a challenge, but one we love to take on! For many, the challenge is finding a decking solution that balances sustainability with longevity, aesthetics and functionality.
What are options for sustainable decking materials?
- Natural Wood Decks
- Treated Lumber
- Composite Decking
- HDPE Plastic Decking
Natural Wood Decks
Natural wood decks have advantages that no other decking material possesses. Wood is nontoxic and extremely strong for its weight. It is beautiful and easy to work with. It is a renewable resource. And as long as the forest has been sustainably managed and the wood has been procured with limited fossil-fuel inputs, it can be a wonderfully green product. It is also relatively easy to reuse in future projects.
The problems associated with wood decking spring from its advantages: the natural inclination of your beautiful wood deck is to return to the soil from whence it came, by the action of weather, insects, bacteria, and mold. To delay this effect, you can choose wood that is naturally resistance to rot and insects, like native cedar and redwood and imported tropical hardwoods such as teak and ipe (a Brazilian hardwood also known as ironwood).
It is worth noting that the famed rot-resistance of redwood is measurably greater in lumber made from old-growth trees. This wood is now unavailable except as reclaimed wood from old buildings. If recycled redwood or cedar is available in your area, it is worth seeking out, both to conserve natural resources and as a superior building material. If you cannot find old growth redwood, you can *seek out sustainably harvested redwood. To ensure that your wood is sustainably sourced, look for wood certified by the Forest Stewardship Council (FSC).
Naturally rot-resistant wood is wonderful stuff, but this type of wood has become increasingly expensive, forcing people to search for more cost effective alternatives. A popular substitute, especially in areas far from cedar and redwood forests, is decking made from less rot-resistant, cheaper softwoods that are treated with chemicals that inhibit decay.
The degree of a woods rot-resistance depends upon the depth of treatment—wood that is in contact with damp soil needs the deepest treatment. Treated decking can be finished with stains and paints much like natural wood (with some adaptation), and it retains all the strength of natural wood.
Slightly less poisonous treatments like amine copper quat (ACQ) and copper azone (CA) are starting to replace older, more toxic options for residential use. The safer alternatives are still far from benign, however. ACQ- and CA-treated wood cannot be recycled or burnt—it’s toxic to produce, work with, and dispose of. Currently the best alternative wood preservative is borate. Borate is water-soluble, meaning that it cannot be used in ground-contact situations, but it is fairly inert and non-toxic.
Composite decking products blend waste wood fiber and recycled plastics, adding in waxes, fiberglass, and preservatives to form wood-like boards. Some products last up to 20 years with little maintenance. However, all will weather, and warping is not uncommon. Composite lumber has some of the strength of wood, it looks and feels very similar, it can be worked with wood tools, and it uses waste products that might otherwise end up in a landfill.
In terms of green building, the biggest objection to composite decking is that, although it lasts a long time, it is very difficult to dispose of once it reaches the end of its life because the biological components (wood and other cellulose) and “technical” components (plastics, waxes, and fiberglass) are blended.
HDPE Plastic Decking
Lumber made entirely from High Density Polyethylene resin— the same plastic that makes milk jugs— is made from waste plastic. Like composite lumber, it is workable with wood tools and is available in a variety of colors and textures.
Plastic lumber does not possess the strength of wood and it is thus best suited for low-load structural applications, such as tables, benches, or planks on well-supported walkways. It is not intended for primary structural load-bearing elements, such as posts, joists, and beams. Manufacturers of plastic lumber vary in their use of post-consumer waste. Look for products that contain at least 50% post-consumer waste plastic.
As we design and modify our living spaces, finding the right decking option for your budget and your values is key, and these four sustainable decking solutions can help you decide which material is right for your needs.
This post was supported by Mendocino Forest Products, supplier of FSC certified redwood. Image from company.