Homeowner’s Guide To Composite Decking

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Composite decking has had more than 20 years to evolve. If you're considering it for your deck project, here's an overview of what's available.

When Trex introduced composite decking in the mid to late 1990s, the company’s name became synonymous with the product, much like Kleenex is synonymous with facial tissue. These days, there isn’t such a direct association, because many competitors have run with the idea of composite decking, and many produce similar products.

In fact, composite decking available today compares to original Trex decking in a way analogous to how contemporary mobile devices compare with the original iPhones. Composite decking was a great idea when conceived — it recycles waste products into a product that outperforms wood, a dwindling resource — becoming an even better one through innovation.

Innovation and improvement of composite decking products has lead to choices for homeowners, whether they want to DIY their deck or hire a contractor to build it. And, there may be situations in which real wood is a better decking choice.

If you’re considering a new deck, or you want to revitalize and existing one, here’s what you need to know about composite decking.

What Is Composite Decking?

Composite decking is manufactured by combining wood waste, such as sawdust and smaller wood dust fibers, with polyethylene plastic. The material is often recycled from plastic bottles and milk jugs. The combination is heated and extruded into standard 1- and 2-inch by 6-inch decking boards, which are often stamped with a wood grain pattern to resemble real wood. Composite decking can be cut, screwed and nailed like wood decking boards, but it can’t be sanded, shaped or power-washed.

Modern composite boards are treated with ultraviolet inhibitors and borate preservatives to resist fading, moisture and mold. (Moisture and mold were the Achilles’ heel of first-generation Trex boards.) Many are capped with a surface layer of PVC to completely seal out the elements.

Composite boards can be solid all the way through, or manufactured with hollow cores making them lighter and saving on materials. Some are milled with tongues and grooves, and some have grooves for fastening to deck joists with hidden fasteners.

Pros of Building with Composite Decking

Because it’s a synthetic product, you don’t have to worry about warping, knots, splits or other defects when working with composite decking. Not only that, you never have to treat it for termites or carpenter ants, because it isn’t susceptible to insect damage. As a building material, it offers these additional benefits:

  • Low maintenance: Composite decking never needs staining or refinishing. You do need to wash it occasionally to keep it looking its best, but you can do that with soap and water.
  • Durable: Manufacturers take great pains to engineer products that outlast wood. You can expect a composite wood deck to last from 25 to 30 years, with minimal maintenance. Hardwood and pressure-treated decking, on the other hand, may last 20 years, if you’re lucky.
  • Nail-free options: Composite boards with grooved edges are designed for use with hidden fasteners. They clip into the grooves and hold the boards securely when screwing them to the deck joists. They’re easy to use and produce a clear deck surface.

Cons of Building with Composite Decking

Composite decking may be manufactured with recycled materials, but it isn’t necessarily a green building product. Old composite boards can’t be recycled and usually end up in landfills, and because of the plastic content, they decompose slowly. Besides this, there are other composite decking drawbacks to consider:

  • Cost: Even with the recent surge in lumber prices, composite decking boards cost, on average, from 15 to 20 percent more than pressure-treated pine, redwood or cedar.
  • Lacks structural strength: Composite decking boards are heavier than wood and tend to sag if they aren’t properly supported. You still need wood to build a deck foundation because composite materials aren’t up to the job.
  • Gets hot: Composite decking boards absorb more heat from the sun than wood and can be uncomfortably hot on sunny days.
  • Absorbs moisture: The wood particles in composite decking boards can swell and turn moldy in rainy weather. Manufacturers minimize this by using less-absorbent hardwood fibers and capping the boards with a PVC layer, but properly weatherized decking boards tend to be more expensive.
  • Not wood: Despite including pigmentation and texturing, manufacturers can’t make composites look 100 percent realistic.

Types of Composite Decking

A few years ago, homeowners could choose from 10 or so different composite decking products. Today, there are more than 50, from manufacturers like Trex, Fiberon, MoistureShield, Cali Bamboo, Duralife, Lumberock, Envision and TimberTech. Each manufacturer tries to put its signature take on the product (Cali Bamboo, for instance, manufactures its boards with bamboo fibers instead of wood).

Homeowners shopping for composite decking will encounter these either/or decisions:

  • Capped or uncapped: First-generation composite decking lacked the protective extruded PVC capping layer of that later became common. Those original boards were subject to moisture deterioration and mold. Capping largely eliminates this problem, but to completely eliminate it, boards must be capped on all four sides. Many products are capped on only three.
  • Grooved or ungrooved: Composite decking boards with smooth edges more closely resemble wood, but they must be face-nailed or screwed, whereas you can use hidden fasteners on grooved boards. Some boards have tongues and grooves and can be assembled into a solid surface like a hardwood floor.
  • Solid or hollow: Hollow boards are lighter and don’t require as sturdy of a foundation.
  • 1 inch or 2 inch: Two-inch composite boards more closely resemble traditional wood decking. One-inch boards are lighter and more likely to have tongues and grooves.

Building With Composite Decking

If you’re going to build a deck, you’ll build the structure with pressure-treated wood, and if you choose composite decking, you won’t find it much different to install than wood. You cut boards to length with a circular saw just as you do wood boards, and if you decide to attach the boards with face nails or screws, you can drive them just as easily into composites as you can into wood.

Hidden fasteners are a key innovation that can actually make composite decking installation easier. You fasten them to the joists, and they clip into grooves in adjacent rows of boards creating a fixed spacing between them eliminating the need to do the spacing yourself. This can be a real time-saver when installing a large deck.

Chris Deziel
Chris Deziel has been active in the building trades for more than 30 years. He helped build a small city in the Oregon desert from the ground up and helped establish two landscaping companies. He has worked as a carpenter, plumber and furniture refinisher. Deziel has been writing DIY articles since 2010 and has worked as an online consultant, most recently with Home Depot's Pro Referral service. His work has been published on Landlordology, Apartments.com and Hunker. Deziel has also published science content and is an avid musician.