Composite Decking – some thoughts and overseas observations

Personally I never liked composite decking.

I am not sure whether people understand the difference between recycling and downcycling. Recycling means (to me) that you can turn a product into the same product over and over again or into another product with equal value or maybe even higher value (that would be upcycling).

However in most cases when I read about recycling, it appears to simply mean molding a high quality product into an inferior product that cannot be recycled any further but will end in the landfill (or in incineration plants overseas).

One of those examples appears to be composite decking, that has entered the NZ market some years ago. It is either manufactured from recycled plastic entirely or with additions of a varying percentage of sawdust. Whatever composition is has, it is a mix of materials and will not be able to be recycled. As a result, you are extending the life of a previously good product (the “raw” material by another 15 years. Some manufacturers used to give you less than 15 years warranty, however according to latest determinations, council can reject a composite decking material when the expected durability is less than 15 years because that’s what the requirement for decking material is in NZ.

Over and above that, there may be some lessons learnt from overseas too:

From: U.S. Consumer Product Safety Commission

NEWS from CPSC, U.S. Consumer Product Safety Commission
Office of Information and Public Affairs Washington, DC 20207
Originally issued August 19, 2005
Last Revised April 28, 2008
Release #05-247

CPSC, Kadant Composites Inc. Announce Recall of Certain GeoDeck™ Decking and Railing Materials

WASHINGTON, D.C. – The U.S. Consumer Product Safety Commission, in cooperation with the firm named below, today announced a voluntary recall of the following consumer product. Consumers should stop using recalled products immediately unless otherwise instructed.
Name of Product: GeoDeck™ Decking and Railing Materials
Units: About 11,000 constructed decks
Manufacturer: Kadant Composites Inc., of Bedford, Mass.
Hazard: When the decking or railing material is exposed to hot temperatures and sunlight, it can prematurely degrade. The degraded material could break, posing a fall hazard to consumers.
Incidents/Injuries: Kadant Composites has received about 370 reports of accelerated degradation of the decking material. No injuries have been reported.
Description: GeoDeck™ is a composite decking product that looks similar to natural wood and is sold in three colors including: driftwood, cedar and mahogany. The decking materials were manufactured between April 2002 and October 2003. Each decking and railing component has a manufacturing date stamp (day/month/year) on the cut end, which may still be visible on uninstalled materials.
Sold at: Retail lumberyards nationwide from April 2002 through July 2005 for between about $2 and $2.50 per linear foot.
Manufactured in: United States
Remedy: Consumers should check their GeoDeck™ decking materials for visible cracks on the surface and check to see if the surface can be easily scratched with a fingernail or the corner of a credit card. However, the firm is out of business and a remedy is no longer available, so consumers will need to arrange for repairs themselves.
Consumer Contact: Firm is out of business. Contact Information is no longer available.

Retrieved from: on 20-02-2009

Composite Decking

By Tim Carter ©1993-2009 Tim Carter

Summary: Composite decking is very attractive but not all composite decking materials are the same. As you start to analyze composite decking prices when you actually touch and feel composite wood decking samples, be sure you ask very pointed questions about what the manufacturer includes in the composite decking to prevent wood rot. Be very careful as some salespeople are armed with the wrong information!

Outdoor deck components including decking, railings, spindles, post wraps and caps, etc. that are made using a mixture of plastic and wood or other cellulose material are a rapidly growing building products category.

You were possibly wooed by the extensive amount of advertising that this industry is spewing out to consumers and contractors alike. Some of this advertising states that the composite decking materials will not rot. These particular claims made by some of the manufacturers, though, may come back to haunt them.

These composite decking materials first started to appear in the early 1990’s, and one of the first manufacturers intended for its products to be very environmentally friendly. They made their composite decking material by combining recycled plastic milk cartons and discarded shipping pallets. Many of the other competing products are now made using virgin plastic and cellulose fibers or flour and/or a blend of virgin products with recycled materials. Some are still made with 100 percent recycled materials.

Depending upon whom you talk to, you will get both positive and negative comments about composite decking. Some homeowners on the East Coast were so unhappy with one of the brands of composite decking, they filed a law suit in a state court. Somehow this case was certified as a class action in that one state. Rather than fight expensive future legal battles in a number of different states, the decking manufacturer decided to agree to a national settlement. By doing this, any evidence or lack thereof concerning the plaintiff’s claims was never disclosed in a public courtroom.

Several renowned scientists have also discussed composite decking materials in three separate professional white papers published between September 2001 and December 2002 in the Forest Products Journal. The findings in these three papers indicated that the wood fibers and other cellulose products used in the composite decking products they tested can and does rot if they’re not treated with a preservative.

At first blush, this may not seem like a big issue; the average person might think that the wood or cellulose content of composite materials is low. But it appears many of the products have a cellulose and/or wood fiber content of nearly 50% of the volume of the product and in some it can climb to nearly 70%. Laboratory tests have shown that some of the composite decking materials can lose between 10 – 20% of their overall weight over time, which translates to a possible 40% or more loss of wood content due to rot.

In an effort to get to the bottom of the issue, I decided to interview 15 of the most prominent composite decking manufacturers. I sent them a series of written questions asking about their products, whether their raw ingredients are virgin or recycled, whether they were aware of the Forest Products Journal white papers, whether they use a preservative in their products and a few other generic questions. Only
one company of the 15 responded, and they provided concise written answers to my questions. I found the silence of the other 14 manufacturers to be very disturbing.

Further investigation revealed there is at least one preservative that can and is incorporated into at least one of the composite decking materials. This simple chemical – zinc borate – can be blended with the wood or cellulose component as the decking is manufactured. The borate in the preservative acts as a poison to many fungi that typically would consume the wood fiber and produce wood rot. The zinc borate preservative is also long-lasting. It can remain active in the composite decking materials for 20 or more years.

Most untreated lumber exposed to the elements rots over time. Don’t think for a moment that the wood or cellulose fibers in the composite decking materials are totally surround and protected by the plastic component. That is not the case. The wood and/or cellulose fibers not only can be readily seen at the surface of the products and at all cut edges, they are randomly interconnected throughout the entire length, width and depth of each board. Water can and does soak into many of the composite decking materials and this water fuels the wood rot process in those materials that do not contain a preservative.

If you are going to use composite decking material, you should consider buying one that contains preservatives. Make the manufacturer prove it to you in writing. Don’t count on the warranty as being proof that a preservative is used. More importantly, be sure to follow the written installation instructions to the letter. Creating gaps between decking boards, spacing of other components and support joist placement are critical. If you fail to install the materials correctly, you or your builder may void the warranty.

Jill, 23 Jan 2008, 15:33
Tim, In 2000 we installed a decking material called “E Wood” on a large front porch. To say the least, we have had nothing but problems with the product. It shrinks so much that we have 1+ inch gaps between the boards. These are now not secure to the supports. The decking is extremely slippery when wet to the point that you have to be holding onto a railing or you will take a fall. It is curling at various places, etc. We have reinstalled the decking three times, with the same results. We’ve contacted the seller (Home Depot) and the distributor (Cascade McFarland) but have yet to receive much help. At the last communication with Cascade we were told that we would just have to live with it.
Have you ever heard of a recall or other actions regarding this horrible decking product? We are open to any suggestions. Thank You, Jill

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