If you've ever wondered what becomes of your recycled grocery bags, check out your neighbor's deck--it might be made of them. More than 70 percent of recycled plastic bags (over 1.5 billion of them!) are converted into composite decking, fencing, and similar outdoor materials by the U.S.'s largest manufacturer of these materials, Trex Company.

Trex and several other manufacturers, including Weyerhauser and TimberTech, combine landfill-bound plastic, wood scrap, and sawdust into low-maintenance outdoor materials that imitate the look of wood somewhat convincingly but are far superior to natural wood in their ability to stand-up against the damaging effects of sun, rain, salt air, and insects. Though not meant for structural purposes, these products are plenty strong for decking, fencing, and railings.

Builders like composites because they are relatively easy to install--the materials are very consistent in size and quality, come in lengths up to 20 feet long, and are not prone to warping and cracking. Composite decking won't rot or splinter (an extra bonus for bare feet). New styles also have fire prevention technology incorporated into the composite which reduces the risk of house fire during cookouts and makes them less of a fire hazard where wild fires can be a threat.

On the down-side, composite decking is susceptible to stains (especially grease stains) and may fade over time. Perhaps the most serious limiting factor is cost. Quality products cost more than softwoods such as treated pine. But they last longer with far less maintenance, so this premium is offset by their durability.

Composites come in both solid and hollow-core versions. Solid "boards" are simpler to deal with, but heavy; hollow types are lighter but fussier to install.

Some composites look like real wood--at least from a distance. For families with young children, these synthetic boards have the additional advantage of being splinter-free. With others, it's best to simply view them as a new material. If you're not satisfied with the color choices, or if you would like your deck to match your house, most products can be stained or painted, as specified by the manufacturer. Some may fade more than others.

Vinyl decking is yet another low-maintenance option, although one that offers a particularly non-traditional deck. Installation differs as well. In general, first an aluminum or vinyl track is installed across the joists, and then top pieces are snapped into place. From an environmental standpoint, composite decking is considered a “green” product because it is constructed with recycled materials and is very durable.