Sustainable Deck Materials

Photo: INC.
The lowdown on plastic decking and natural, pressure-treated and composite woods.

We want our decks to last for years, keep their color for years, provide a platform for backyard fun... for years. But how can my deck sustain sustainably? Wood naturally wants to rot when cleaved from its roots and milled to a svelte six-inch deck board. Yes, we've found ways to seal wood and stave off rot, but most of these have harmful environmental effects – helping to sustain the deck but doing so unsustainably.

We've even discovered and developed alternatives to wood, using everything from wood waste fibers to recycled plastics, but there is no perfect solution for building an eco-friendly deck or for greening your existing deck. In fact, given the availability of low-cost, low-maintenance, non-toxic and recyclable concrete, tile and natural stone, the greenest backyard deck may be the one never built at all.

But before we get too drastic, let's explore the several "sustainable" deck options before us…

Natural Wood

Wood is still the most natural choice. It grows abundantly all around us, is easily recyclable, and certain species, such as cedar and redwood, are naturally rot-resistant. Wood is a sustainable resource, if harvested properly. The problem is that forests around the world are being rapidly cut down or degraded through mono-cropping. That fact has also made naturally rot-resistant woods more expensive, forcing many homeowners to opt for cheaper, chemically-treated woods. Even cedar and redwood decks usually require a sealant of some kind that can be harmful to the environment as well.

There are ways to maximize the greenness of your natural wood deck, the most prominent being an understanding of the entire life-cycle of the product. Know where it came from (imported or long-traveling woods require a lot of energy and pollution in transport), and know where it's going when it "dies" (wood is recyclable, but you'll need to make sure it gets to the recycler someday).

This understanding of a product's life-cycle is essential to properly choosing any of the green decking materials discussed here.

Pressure-Treated Wood

As briefly mentioned earlier, the relatively high cost and scarcity of natural wood products like cedar and redwood have fostered the rise of pressure-treated (PT) lumber. These are softer, less resistant woods that are chemically treated to repel insects, rot and mold. PT can also be treated with stains or finishes much like natural wood.

This cheap and long-lasting result is enticing, hampered only by the toxic chemicals injected into the wood – chemicals neither good for the environment nor you. In the old days, chemicals like creosote and chromated copper arsenate (CCA) were used. Today's chemicals, like amine copper quat and copper azone, are less toxic but still far from environmentally friendly. All pressure-treated woods are toxic to produce, handle and dispose of, and cannot be recycled or burned.

Borate is the one wood preservative that is nontoxic. However, it is water-soluble and cannot, therefore, be used in situations where it would come into contact with the ground. Other tricky areas (even if just using it for decking) would be near siding, in corners and other areas where ground contact may not be an issue, but trapped rainwater and debris may be.

As of this time, pressure-treated woods, whether borate or arsenate, are probably not your best choice in green decking. Perhaps innovation will spawn soon from the increased demand for long-lasting, green deck materials. But in the meantime, on to another recent up-and-comer…

Composite Wood

Composite wood decks have risen to prominence over the last decade or so. They are made from waste wood fibers and recycled plastics, such as grocery bags, that might otherwise have seen a landfill. They are fairly strong, can last many years with little or no maintenance and are virtually stain-free. They are susceptible to weathering and warping over time but, if properly installed, can last for 20 years or longer with little worry to the homeowner.

The one eco-downfall of composite decking is disposal at its life's end. During production, the wood fibers, which are very much recyclable, are inextricably bound with the non-recyclable plastics. Therefore, composite decking is very hard to get rid of without dumping, resulting in the postponement rather than cancellation of the materials' trip to the landfill.

As of yet, there have been no breakthroughs in finding a way to recycle composite decking when its lifetime ends. Nevertheless, it does have its environmental benefits, the biggest of which is that no new trees are cut down to produce it.

Plastic Decking

There is also decking made from HDPE, or High Density Polyethylene resin. It is the same plastic used to make milk jugs and is made from plastic waste, giving it its green edge. It is fairly easy to work with and requires no special tools beyond woodworking tools. However, plastic decking is nowhere near as strong as wood, and should only be used as decking or in other non-load bearing situations.

HDPE boards expand and contract quite a bit with temperature changes and have an increased tendency to warp. Also remember that these boards are not made from 100-percent recycled plastics, and manufacturers differ in their use of post-consumer content. HDPE decking that is at least 50 percent post-consumer plastic is a good benchmark, although it’s important to remember that plastic is petroleum-based and a good deal of fossil-fuel energy goes into the creation of plastic products.


Aluminum is also available. It is low-maintenance, made from recycled products and can be easily recycled itself. Aluminum decks can be made to look like natural wood and the deck boards interlock to create a water-resistant barrier. Because the aluminum disperses heat, it will also stay cool to the touch, even in areas under direct sunlight. No coatings or sealants are necessary and decks often come with lifetime warranties.

Sealants and Preservatives

If you already have a wood deck, or if you're looking to preserve your newly completed project, then finding a green way to preserve that deck may be your top priority. A natural stain or finish is not so difficult to find as it used to be, although almost certainly more expensive. Still, low-VOC and low-toxic finishes are available.

Dan harding Dan Harding is a well-versed veteran of solar critique, commentary and reporting. He has published well over 1,000 articles on a wide variety of solar industry topics, ranging from cutting-edge technology and gadgetry to political satire and powerful editorials. CalFinder is proud to tout Dan as our resident solar expert. He holds a B.A. in English from Michigan State University, and enjoys reading, writing and home construction.