Replacing Wood Structures with Plastic Lumber in City and State Parks
written by: Erik Hinrichsen•edited by: Lamar Stonecypher•updated: 6/20/2011
This article provide helpful information about the advantages and drawbacks of using plastic lumber for park site amenities and municipal structures such as picnic tables, benches, fences, docks, and decks.
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Many of the parks in the United States - be they state, national, or municipal parks - were built during the thirties and forties as part of efforts to alleviate the economic depression. These park sites were built out of a material that is both cheap and plentiful- lumber. Lumber, however, is not a long-lasting construction material. Most parks have had to replace or rebuild amenities one or more times already, and this replacement comes at considerable expense. Park administrators interested in an alternative to lumber may be interested in recycled plastic lumber, a long-lasting product with qualities similar to natural wood.
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Benefits of Plastic Lumber
The biggest advantage of plastic lumber is that it is rot-resistant. Today's plastic lumber materials require little to no maintenance and are extremely resistant to rotting, even in wet environments. The material also resists splintering, cracking, and peeling. Ants and other insects cannot penetrate plastic lumber; neither can bacteria nor barnacles.
Plastic lumber is also resistant to fire, and usually extinguishes itself quickly. In addition, graffiti is easy to remove from the surface of plastic lumber materials.
There are several environmental advantages to using recycled plastic lumber for park site amenities, as well. Unlike rot-resistant treated woods, plastic lumber contains no toxins or heavy metals. Plastic lumber also provides a use for plastics that would ordinarily go into landfills, where they take thousands of years to decompose.
Finally, and most importantly, there are the cost considerations. The initial cost of plastic wood is typically higher than that of traditional lumber. Because plastic lumber lasts longer and requires less maintenance, it ultimately costs significantly less than traditional wood options. Moreover, the price of plastic lumber is likely to continually decrease, as it is a relatively new material.
Plastic lumber is made from recycled plastic materials, most typically high density polyethylene (HDPE). The plastics are shredded and mixed with various stabilizers, then extruded into the usual lumber shapes. There are several types of plastic lumber, with versatile properties, on the market today.
This variety is composed solely of HDPE and stabilizers. Though it is structurally different from wood, the all plastic variety of lumber can often be substituted for wood and is a popular choice in decks or docks.
This material is a composite of plastic and some fibrous material, usually sawdust, in a 1:1 ratio. These materials are stiffer than the all-plastic variety, but also cheaper. However, they have some of the same tendency to rot and stain as ordinary wood. This can be a good option because it looks more natural than all-plastic lumber.
Fiber Reinforced Plastic Lumber
This is the most expensive variety of plastic lumber. It consists of plastic mixed with glass fibers, which may be chopped or continuous. This type is strong enough to be used as a structural material.
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Comparison to Traditional Lumber
Plastic lumber has a number of advantages over natural wood, but may have some drawbacks. Plastic lumber may not look as "natural" as traditional wood; some park visitors may prefer the look of natural wood to that of plastic lumber. Plastic lumber may also have a tendency to retain heat more than ordinary lumber due to its darker color, so it can be uncomfortably hot on sunny days. In addition, the initial cost of structural plastic lumber is fairly high.
For information on ASTM standards for recycled lumber, see the sources below.