Plastic Deck Lumber: What to Know Before You Buy

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The pleasures of having a wood deck on your house are counterbalanced by deck maintenance. Wood deteriorates—it's just a natural thing. Deck maintenance is all about slowing that natural process with regular staining and sealing. As exposed as they are, floorboards especially bear the brunt of the weather. Isn't there a way to slow down the deterioration more, and without all of that staining and sealing?

Plastic deck lumber is one of the best alternatives to traditional wood decking, along with composite and aluminum decking. If you're looking for deck material that's durable, low-maintenance, and never needs to be finished, plastic lumber may be right for your deck.

What Is Plastic Deck Lumber?

PVC Decking

The type of deck lumber often called plastic lumber is made from either recycled plastic or from new materials, typically single resin polyethylene (HDPE and LPDE), polystyrene, or polyvinyl chloride (PVC).

PVC plastic decking appeared on the building material market in the late 1980s and is available in dimensions similar to traditional lumber.

Plastic lumber has other applications besides decking, include trim boards, railings, outdoor furniture, siding, and fences. One thing you cannot use PVC for is structural applications, so the support posts, joists, and beams of a deck must be built from a different material, usually wood.

Plastic lumber has the reputation of being durable forever. Plastic lumber is durable since it does not absorb water. Since it contains no organic materials, it cannot rot. But plastic lumber does not last forever. After being exposed to the sun and other elements for long enough, plastic lumber may peel or crack. Its color will eventually fade. Unlike wood, which can be sanded and re-stained, plastic decking offers no such repair alternatives: It can only be replaced.

Composite Decking

Plastic decking is not the same thing as composite decking, which is made of plastic and wood fibers. In many cases, up to 95-percent of the plastic used is from recycled materials. Plastic decking is only plastic, although it can have any number of additives for resistance to sun damage, scratching, and weather.

With composite decking, the plastics polypropylene or polyethylene link with the wood fibers for a strong bond. They also help to create a richly textured surface with color that more closely resembles wood than PVC decking.

PVC-Wrapped Composite Decking

A combination of PVC and composite decking, this material has a composite core that is wrapped in PVC.

Pros and Cons of Plastic Deck Lumber

Pros

  • Can be molded into many different shapes and sizes, including curves
  • Waterproof and resists rot and mold without sealant
  • Stain-resistant against many chemicals and substances
  • Manufactured in a range of colors
  • Short-term fade-resistance
  • Does not contain chemical treatments
  • Does not splinter
  • Resists insects
  • 100-percent recyclable
  • Comes with a manufacturer's warranty

Cons

  • Slippery, especially when wet
  • Weaker than wood, so shorter joist spanning
  • Can look artificial
  • Uniform texturing
  • Cannot be stained or painted (even if you want to)
  • Subject to fading in the long-term

Installation

Plastic lumber can be cut and drilled like wood. No special tools are required. This makes it an option for do-it-yourself installation. It can be screwed down to a wood deck structure, just like wood decking, but many types of plastic decking are designed for hidden-fastener systems that leave the top of the decking unmarred by screw heads.

Keep in mind that plastic isn't able to span as far as wood, and you must provide adequate support for the decking boards. Also, leave room for the plastic boards to expand. For these and other reasons, like maintaining the warranty, it's important to follow the manufacturer's installation specifications.

Cost

Both plastic lumber and composite wood-plastic lumber cost more than wood decking. You will recoup a large portion of these upfront costs since plastic deck lumber is so low-maintenance compared to wood and likely will have a longer lifespan.

Generally, plastic deck lumber will cost $9.50 to $15 per square foot, installed. Composite decking will cost around the same: $11 to 15 per square foot.

For an accurate cost comparison with wood decking, factor in the cost of periodic finishing that wood decking requires. Wood decks should be re-stained or sealed every two to three years in most conditions. The cost of materials adds up, as does the labor or the time if you're doing the work yourself.