Gardening Articles: Landscaping :: Yard & Garden Planning

Would-Be Wood (page 3 of 3)

by Alex Wilson

Using Plastic Lumber

Although not as common as pressure-treated or cedar lumber, more and more recycled-plastic lumber is being used around homes. Decking is the most common use. Plastic lumber replaces pressure-treated wood, and premium rot-resistant woods such as cedar, redwood, and teak.

In landscaping, recycled-plastic lumber, including commingled plastic products, can be used in retaining walls to stabilize steep slopes. The landscape timbers are bolted together or pinned into the ground. In gardens, plastic lumber is an alternative to preservative-treated lumber, for providing stakes, garden edging, and support for raised beds.

Another important application is for outdoor furniture such as picnic tables, garden benches, and lawn chairs. This furniture may be a little heavy, making it difficult to move around, but it won't rot and should last for years.

Recycled-plastic lumber, both products made from 100 percent plastic and from wood-plastic composites, can be installed using ordinary carpentry tools, though carbide blades are recommended for circular saws. (The plastic may melt or burn if a dull blade doesn't cut through it quickly enough.) All will accept nails, but stainless steel screws in predrilled holes are recommended.

Deck planking is the most commonly available material. It is usually noted as "5/4-by-6," a shorthand for 1-1/4-by-6 (actual dimensions 1 by 5-1/2 inches), and is available in various lengths. All require posts and supports made of pressure-treated wood (or Carefree Structural Lumber).

Compared to wood, plastic and composite lumbers are heavier and more subject to thermal expansion and contraction. Depending on the kind of wood being compared, plastic can weigh two to three times as much. Be sure to check manufacturer's specs regarding the size of gap to allow between boards both width-to-width and end-to-end. Most products specify a minimum width-to-width gap of 1/8 inch, plus another 1/8 inch for every 20-degree difference between installation temperature and possible maximum temperature. Basic end-to-end gaps are typically 1/16 to 1/8 inch; longer boards may need more.

When working with plastic woods, always wear a dust mask and work in an area with adequate ventilation. While it's not necessary, most can be painted or stained, though they won't hold the finish as well as wood does. Decking that is 100 percent plastic cannot accept paint and stain.

Four Kinds of Recycled-Plastic Lumber

* SmartDeck is made of high-density polyethylene and oak sawdust. It fades to a warm silver gray. A 16-foot 5/4-by-6 costs $25 and weighs 43 pounds.

* ChoiceDek Classic is made of high- and low-density polyethylene and red cedar chips. It fades to silver gray. A 16-foot 5/4-by-6 costs $25 and weighs 33 pounds.

* Carefree Decking is made of high-density polyethylene. It's available in five non-fading colors: light gray, light silver, red-brown, beige, and white. A 16-foot 5/4-by-6 costs $28 and weighs 20 pounds.

* Trex is made of high- and low-density polyethylene and sawdust. It's available in tan and dark tan, both of which fade slightly, and dark brown, which is non-fading. A 16-foot 5/4-by-6 costs $23 and weighs 40 pounds.

Alex Wilson is editor and publisher of Environmental Building News, a monthly newsletter about environmentally responsible design and construction. He lives in Brattleboro, Vermont.

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