Composite Wood Decks – Testing and Evaluation

by Brad Wear

One of the most popular items on a home is its deck or porch. People around the world have enjoyed sitting outside in the morning or evening for generations. Families and friends make memories on their porches by sharing meals, laughter and stories at the end of the day, or on a weekend. Since the porch (or deck) plays such an important role in life, many people spend hundreds or thousands of dollars on deck construction and maintenance every year. Wouldn’t it be nice if there was a way to enjoy our decks and porches without spending hundreds of dollars and many hours of time maintaining and caring for them?

Advancements in technology are not just limited to cell phones and computers.  New building processes and materials are being developed every year. Composite wood is a great example of modern building material technology and was first used in decking in the 1990’s (http://www.strongtie.com/ftp/articles/fasteningcompositedecking-article.pdf). Initially, while the decking was low maintenance and weather resistant, it was susceptible to warping under heat. Over the last decade, improvements to the material and construction of the board have helped to reduce the amount of warp in composite wood.

Like any building product, composite wood must be evaluated for its mechanical properties under a variety of scenarios. Temperature and moisture effects, freezing and thawing, creep, flexural strength, slip resistance, concentrated loads, stair tread usage, and more, must be determined through independent, third party testing in order determine if the product (either the initial composite wood, or the final, constructed deck board made of composite wood) is code compliant and can be safely used in home construction.

Composite wood deck boards are evaluated through:

• Flexural tests
• Temperature and moisture effect
• UV resistance test
• 2000 hours of accelerated weathering followed by comparison flexural test   

• Freeze-thaw test
• Bio-deterioration tests
• Fungal decay resistance
• Termite resistance
• Creep-recovery test
• Creep-rupture test
• Mechanical fastener holding tests
• Slip resistance testing

Additionally, if the composite wood is formed into guardrails, it must undergo testing for:

• Concentrated and uniform loads
• One and two family dwelling requirements

Composite wood has been gaining in popularity since its first appearance, in spite of the higher cost associated with composite wood construction. This is due to several advantages – composite wood decks are very low maintenance, requiring a simple wash on occasion rather than yearly scrubbing and staining (this can be hundreds of dollars and many hours per year). It also is resistant to a variety of environmental issues, like weathering and bugs, so you save on replacement costs for rotting, uneven, or insect-damaged boards. It is resistant to mold, mildew, and splinters; helping to make it safer. Plus, being made of recycled materials has an added “Green” building benefit.  It has also been shown to increase the value of a structure, offering an estimated 62.8% Return on Investment (Remodeling Magazine, 2012). Given these advantages, it is easy to see how over a few years, the cost of the composite wood deck can be less than that of a traditional wood deck! Because of this, more composite wood manufacturers are entering the market. Make sure your composite wood product stands out from the crowd by participating in a certification program that will verify your products’ claims to durability, safety and beauty.

For more information on Composite Wood Testing, or Composite Wood Decking requirements, please feel free to contact NTA.