On Deck With Durable, Environmentally Friendly Composites
September 2010By Brent Gwatney
In recent years, demand for wood-plastic composite decking has increased rapidly because of its benefits as a durable, long lasting, and environmentally responsible alternative to traditional decking materials. Advances in performance and appearance have expanded product lines and applications, making it a popular choice for commercial deck, dock, and boardwalk installations.
Suitable for a variety of climates—from harsh weather-exposed waterfronts to demanding snow-covered altitudes—wood-plastic composite decking provides contractors the design flexibility, consistent performance, and green benefits their projects require.
To help select among composite decking options and ensure design goals and expectations are met, below are a few characteristics to consider.
ENVIRONMENTAL FACTORS
Most composite decking products are manufactured using a blend of polyethylene plastics and wood fibers. Depending on the manufacturer, some brands contain recycled materials like plastic bags, milk jugs, and reclaimed wood fiber. If composite decking is made with recycled content, contractors should confirm how much, as the percentage of recycled materials can vary from a small amount to between 90 to 95 percent (additives and color agents are typically included, preventing them from being considered 100-percent recycled content).
In addition to the percentage of recycled content, find out how much of the recycled materials are from pre and/or post-consumer waste. Pre-consumer material is manufacturer waste like wood pallets, scraps, and saw dust. Post-consumer material is waste that has been used by a consumer, disposed of, and diverted from landfills.
Because it is harder to obtain and recycle and more likely to end up in a landfill, post-consumer waste is considered to have greater environmental benefits. Wood-plastic composite decking with high post-consumer recycled content like MoistureShield® can help contribute toward green building rating points in LEED® programs.
DURABILITY
The plastic in composite decking acts as the binder, while the wood fibers add strength, stiffness, reduce flammability, and give it the look of natural wood. Most commonly, manufacturers mix wood fibers with plastic and then heat and extrude the material into deck boards. Because each manufacturer has its own process, composite decking products differ in makeup and plank profiles.
How well the plastic surrounds and bonds to the wood fibers during the manufacturing process can significantly impact the long-term integrity of the decking, as the plastic is what protects the wood fiber from moisture. Should wood fibers in the deck planks be exposed over time, they can discolor and begin to rot.
To prevent exposure of wood fibers, MoistureShield’s processing technologies incorporate a unique “total encapsulation” method wherein wood fibers are aligned and completely surrounded by plastic. The finished product absorbs substantially less moisture than other composites and solid wood, and has greater resistance to rot and insects. These factors allow the composite deck planks to be used in applications that have direct contact with the ground (such as landscape trim) and water (like marina decking, dock surfaces, and commercial boardwalks).
Compared to all-plastic decking, composite products provide lower thermal expansion, further supporting the material’s performance in harsh environments. Composite decking also resists splintering, twisting, splitting, and cracking. Under typical conditions, composite decking is expected to last two to three times longer than traditional wood decking materials.
AESTHETICS AND DESIGN
Due to advancements in technology, manufacturers have been able to make composite deck boards that closely resemble the appearance of real wood. However, some brands come closer than others. Contractors should see and feel a deck plank before making a final decision to confirm that its texture and appearance will meet design goals. Keep in mind most composite decking will weather to a slightly lighter shade within the first 6 months of installation.
Composite deck planks are available in solid, ribbed, or hollow profiles, and with or without grooved sides for hidden fastening systems. Solid boards are the most similar to working with wood and don’t require trim or end caps.
The way composite decking is made allows it to be shaped, cut, and designed in ways that are not possible with lumber. With color choices ranging from gray to warm, multi-dimensional hues of tropical hardwoods, contractors and designers have the option to mix and match multiple colors to create unique deck designs, as well as complement existing structures.
Composite deck boards can be bent for use in such applications as stairs, benches, and walkway arches, and any surface or non-structural features that call for round edges. This enhanced flexibility can save contractors time and trouble when building complex deck and dock designs that include curved planks.
To help contractors create and visualize what a completed deck will look like, some manufacturers offer online deck design tools. For example, MoistureShield’s “design a deck” feature and DeckVision™ Design Tool are free programs provided on its Web site (www.moistureshield.com) that allow users to create, save, and edit their 3D deck designs. These tools also show available colors and enable users to explore different color combinations. They provide a way for contractors and their teams to be on the same page before deck installation begins, helping the design and construction phases go faster and smoother.
INSTALLATION
Understanding local code regulations and substructure requirements for spans is essential with composite decking. It should always be installed according to manufacturer instructions, with close attention paid to maximum allowable uniform live load and member span requirements.
Composite materials are easily machined and can be installed with standard hand and power tools. As the material has no grain, it will not split. Nails, screws, and hidden fastening systems are available to attach composite planks, but not all composite decking is compatible with each method. Be sure to check with a dealer and follow manufacturer recommendations.
Composite decking may not require preservative treatments, water sealing, or staining, but all decking should be periodically cleaned according to manufacturer recommendations to maintain aesthetics and prevent mold and mildew. Commercially available deck cleaners are generally suitable. Warranties vary by manufacturer—read through them carefully to determine what is included and covered.
With the growing interest in providing durable, environmentally sound alternatives to conventional building materials, engineered products like wood-plastic composite decking and railing are emerging to fill the niche. These products offer strength and long-lasting beauty, while making efficient use of recycled materials. ■
About the Author:
Brent Gwatney is vice president of sales and marketing for MoistureShield composite decking. For more information, call 866.729.2378 or visit www.moistureshield.com.
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