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Composite & synthetic decking durability research results. Studies of the durability of composite lumber used for decks, ramps, and similar structures show the effects of moisture, freeze/thaw cycles, sunlight, temperature variation, and other factors that impact the appearance, durability, life & safety of plastic & synthetic decking.
Our page top photo shows the collapse of plastic-synthetic deck boards at a New York home while below we also include images of more contemporary plastic type deck boards.
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As our photos show, below, even though synthetic decking material may itself be durable, if the deck is not properly constructed there is risk of rot, and even collapse. At below left is a picture of more recent composite decking at a New York lumber supplier. This deck has been exposed outdoors continuously for several years. At page top and at below right we illustrate an older synthetic or composite deck board product that has failed.
While we knew that this entry deck at an upstate New York home was in bad shape, just how horrible it was was not completely apparent until demolition was begun during a home renovation.
The composite decking shown at left was installed directly over a pre-existing and rotted deck structure - not a smart idea.
This composite deck board photo shows that the deck actually collapsed during work on the structure, revealing rotted wood structure over which the deck boards had been added as a "repair". Luckily no one was injured.
Don't do this.
Research on the Durability of Composite & Synthetic Lumber Reports on Freeze/Thaw, Moisture & Temperature Effects
4/11/2014 bill c said:
We are about to replace a front porch and we are considering using composite boards. do you know of any manufacturer that we should avoid because of poor results and durability?
Bill, it's a topic worth some research, and indeed there have been a number of studies of the durability of composite lumber or "synthetic" lumber. Just above you can see illustrations of some early composite lumber that didn't fare so well.
Current suppliers of composite and plastic decking materials are listed along with their contact information at SYNTHETIC & COMPOSITE DECK SOURCES .
Experts from a variety of fields including the U.S. Forest Products Laboratory, the wood composite manufacturers, and the plastics industry have studied important synthetic-deck board and other composite lumber properties & durability including the structural strength, fire resistance, weathering, color fading, and other properties as well as studying the usefulness of protective coatings on these products.
A scan of recent research suggests that the effects of freeze-thaw cycles on composite lumber as well as effects of moisture, high temperature, and possibly sunlight seem to vary more by the mixture of composite ingredients than to point to a specific brand.
Pilarski and Matuana conducted some important research into the durability of wood-flour composite lumber in 2005 and 2006, listed in the citations below. Note this conclusion:
That we need to read studies of composite lumber performance with care and to make note of just what ingredients are in use is evident in a very different finding by Ronald Wolfe and Agron Gjinolli in a February 1999 USFPL research report.
As a point of comparison with composite lumber typically used for deck or ramp boards, we report here as well on Green (2003) who examined the comparative effects of humidity and temperature on solid sawn lumber and (wood) composite lumber (LVL and LSL) used as structural members.
Finally you might want to take a look at Douglas Gardner (et al)'s research on the use of protective coatings for composite wood products, Gardner et als. (2001 & 2003) and at Stark & Gardner (2008) USFPL from whom we quote just below.
Later work by Morrell, Stark et als (2011) continues this investigation. They conclude:
Here are some references on the durability of composite lumber that you will want to review:
Deck & Porch Industry Associations
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