Professional composite decking. Fiberon via Flickr Creative Commons
Professional composite decking. Fiberon via Flickr Creative Commons

Tell dealers a species or grade of wood and, more likely than not, they can envision exactly what you're talking about and detail its qualities. But then try asking them to explain what makes one brand's wood-plastic composite (WPC) or polyvinyl chloride (PVC) decking or trim different from another. A lot of them will be stumped.

Arguably, no other product in a lumberyard matters so much financially to dealers and yet is so little understood as composites and PVC. At the same time, it's likely that no class of products has grown up so fast. The $1.1 billion composite and PVC decking and railing industry still is in its teens. And like many teenagers, it's a gangly mix of impressive achievements and dumb errors, a body on which onlookers project a lifetime of achievement based on a scant history of actual performance.

A cellular PVC-based alternative decking. Fiberon via Flickr Creative Commons
A cellular PVC-based alternative decking. Fiberon via Flickr Creative Commons

Similarly, PVC trim is expected by 2014 to surpass metal as the No. 2 material used. And while its performance also has improved in the past decade, it still struggles to beat problems caused by thermal expansion, not to mention holding prices in an unsettled raw materials market.

Manufacturers' past claims (hyped by the press and public) that WPC and PVC were maintenance-free certainly helped confuse things, and intense competition has led producers to be intentionally vague about what's in their products.

Should you demand to know what's in this stuff? Well, since 2004, seven wood-plastic composite manufacturers and suppliers have faced lawsuits related to a host of problems, including fading and color changes, slippery surfaces, shrinkage, swelling, and mold. In at least two of those cases, a supplier and reseller were accused along with the manufacturer.

It takes some work, but you can learn to spot the differences between products and, hopefully, avoid future callbacks. Here's a start.

As Much Art as Science

Creating composites and PVC often is compared to cooking, but lots of chefs would be sorely tested if they tried to whip up a deckboard or piece of trim. That's because, unlike in a kitchen, you can't count on the ingredients to be consistent from one day to another.

Wood and plastic typically make up roughly 85% to 95% of the ingredients' total weight. Most of the wood consists of cast-offs from flooring factories. And except for virgin PVC flakes, all the plastic had a previous life as well. WPC and PVC manufacturers work constantly to get reliable streams of raw product, but if the wood flour has a different mix of species or the recycled plastic shipment was heavier on low-density polyethylene film, the manufacturer may need to adjust its formula.

Technology challenges are no less daunting. Consistently and accurately extruding a product–basically, cramming a hot, doughy mixture of plastic and wood through a specially shaped opening–is hard enough. Co-extrusion–pouring a syrupy plastic shell over the inner core in such a way that it bonds exactly where you want at exactly the right thickness–is an added challenge that manufacturers didn't feel comfortable producing commercially until a few years ago.

"It's not a highly repeatable process," says Tom Gramlich, chief operating officer of TimberTech, which makes composite and PVC decks, porches, railing, and trim. "Every night, our operator is fighting a different set of circumstances than the night before."

You can tell how tricky a business this is through the scrappage rate: Industry-wide, manufacturers say, roughly one-eighth of what's produced gets rejected before it ever leaves the factory.

Production techniques also matter. For instance, take the debate over using Celuka. . It's an option used for PVC products that gives the outside of what's extruded an extra-hard surface. Gossen Corp. particularly likes this method when it needs to make sure the object produced meets tight specifications, such as replacement window trim. Jackson Chen of Inteplast, maker of Tufboard products and CEVN decking, shows off his Celuka products by knocking dents into trim made using the freefoam process.

Versatex president John Pace isn't impressed, particularly since his company's goal is to make a product that cuts and nails like wood. "You're trying to make trim, not a brick," he says. "To me, that (Celuka trim) isn't wood."

Manufacturers likewise snipe over the choices that decking producers made with their manufacturing processes. Lately, the biggest argument is over capstock–the plastic substance that has recently begun to be applied to composite decks, giving the products added protection, more intense faux-wood-grain finishes, and ever more varied color options.Capped composites are one of the hottest categories within decking, with sales rising six-fold in popularity last year, according to a new study by Principia, a research group. Meanwhile, demand for cellular PVC decking rose 40% last year. Together they constitute decking's ultra-low maintenance segment, and Principia estimates their share of the total $1.1 billion market for non-wood decking and railing has risen to 45% today from 15% in 2008.

Some firms put the capstock completely around the inner core, some skip covering where hidden fasteners go, and others leave one side untouched. All argue that these choices can result in big differences in how the products perform–stressing, of course, that their choice is what's best. But for the most part, it's still too early to tell which manufacturer is right.

Cost vs. Quality

What is certain is that making WPCs and PVC products requires a careful mixing of ingredients not just for performance, but for cost. One way to do that is by literally trimming away some of what's produced. It's a principal reason why a lot of lower-priced composite decking is flat on just one side and scalloped on the other–you use less mix to create a board.

Polyethylene and PVC today typically are made from extracts of natural gas rather than petroleum, but pricing still goes up and down with the oil market. Added cost pressures have arisen from this year's earthquake and tsunami in Japan, which knocked some processing plants offline. You can supplement U.S. PVC production by getting it from China, but plants there make a dirty product that requires a lot of titanium dioxide to whiten it–and titanium dioxide is in short supply. Meanwhile the recession has slowed business at the flooring and cabinet shops that generate most of what becomes wood flour.

Advanced Environmental Recycling Technologies (A.E.R.T.) has found other ways to limit cost runups. It gets its plastic from recycled goods rather than virgin PVC, and over the years it has learned how to convert ever-lower grades of polyethylene into usable feedstock. (Trex also gets most of its plastic through recycling.) As for wood flour, generally the more finely ground it is, the more expensive it gets. A.E.R.T. uses relatively large flakes of wood. The result, however, is a rougher-looking board than its competitors.

But if you really want to scrimp, ultimately you need to examine your additives–the chemicals that make trim whiter, deckboards stiffer, cores less (or more) foamy, and surfaces less likely to fade in the sun or crumble. Like spices, a little additive can cost a lot. Bill Ross, vice president of sales at Fiberon, says that while wood flour can cost 10 cents a pound and virgin PVC a dollar a pound, an additive can set you back hundreds of dollars per pound.

Anatole Klyosov, a biochemist and former WPC executive, says several lawsuits this past decade involving WPCs appeared to arise from failure to use enough additives. In one case, he says, a manufacturer didn't add enough color pigment, thus leading to fading. Another case stems from a lack of antioxidants.

"I'm astounded that we sold as many boards as we did five years ago," one decking exec says. "Because five years ago, those boards didn't do what they promised."

Some manufacturers expect the number of lawsuits eventually will drop because of capstocks. Why? Think of an M&M.

Just as putting a hard candy coating around an M&M's chocolate core protects the insides, manufacturers say pouring a cap around a WPC center protects that core from what in the past has led to its demise. "Wood fiber is the root of all problems" in WPCs, says Peter Gallagher, manager of sales development at Polyone, a leading formulator of additives. It's what in the board (that) is susceptible to bleaching from the sun, decay from the wet, and consumption from the mold, while tannins in the wood flour can get out and stain the composite.

Capstock's advocates regularly say that adding this armor coat to the board significantly improves its long-term performance. What they bring up less often is that using capstock could make it possible to slack off a bit on what's inside–there's no need to put in coloring there, for instance. Whether firms actually are cheapening the insides remains an open question that likely will take years of field testing to determine.

For its part, Trex maintains that the core of its capped decking, Transcend, is exactly the same as its uncapped Accents line. "We don't have the philosphy that you can junk up the core," says Kyle Lancaster, Trex's director of technical services.

Trex may be open on that issue, but it's close-mouthed on what's in its capstock–so private, in fact, that it won't even say whether the capstock is animal, vegetable, or mineral. It just calls it a "shell." You also can't learn more about the capstock by examining a patent; like the formula for Coca-Cola, Trex's recipe for the "shell" is a company secret.

Such secrecy is quite common among decking manufacturers. Examine Material Safety Data Sheets for most of the major WPC and PVC products in the business and you'll find that many list up to 50% of their ingredients as "proprietary." At least one doesn't reveal any at all. And a lot don't even reveal they put in any additives.(See How To Make Plastic Wood)

On the other hand, reading manufacturers' warranties can give you a sense of what these firms believe their products can do–in contrast to the advertising claims they make. Pick up a Trex brochure for Transcend and you'll see on the cover a boast that Transcend "Resists everything but stares." But then go to its 25-year fade and stain warranty, and you'll see language that makes clear its resistance is limited pretty much solely to permanent staining from food and beverage spills.

Meanwhile, TimberTech considers its warranty voided if you use a snow shovel on it. And Deceuninck's Solstice decking, whose brochure declares it offers "The best performance under the sun," warns that you won't get repaid if you spill and then leave plant food on the deck or your dog makes a deposit that goes unnoticed.

Pace is amused by the trend among manufacturers to giving warranties stretching 25 years and longer on products that only came out in the Obama administration. "They make a product and throw it up on the wall and if it sticks, they market it," he says. "Look at some of these decking products that failed. Why did they fail? There's no long-term test data."

Can Testing Be Trusted?

In fact, the testing protocols that companies use to justify their 25-year warranty claims are getting questioned. Historically, to estimate potential wear and tear on composites, manufacturers and academics applied the same testing standards used for treated, solid-sawn wood. But at an international conference on WPCs last month in Madison, Wis., a researcher from the federal Forest Products Laboratory said in effect that you can't subject factory-fresh composites to those tests and get real-life results; the composites have to be "conditioned"–i.e. knocked around a bit–before being put to any tests intended to help predict a product's long-term performance.

When it comes to creating vs. adequately testing new products, "Manufacturing went faster than science could catch up," said one conference participant who specializes in polymer engineering. "What we're now learning would have been nice to know 10 years ago." New testing standards could take effect later this year.

One hoary business maxim is that a lot of competitors will pile into a new market and that, over the years, a few will rise to lead the market, a few others will hang on, and the rest will quit. The WPC decking and PVC markets appeared to be going that way, such as when CorrectDeck sold out last year to GAF. Principia says the top four players in the decking market have increased their market share from 65% in 2008 to 75% today. But lately some new players are coming in that could shake up the situation.

A notable arrival is Inteplast, which makes several private-label brands and has become the licensed producer of CEVN, a PVC decking in which each board has two colors. Meanwhile, Deceuninck made a splash at this year's International Builder's Show with a brand of PVC decking. And Wolf, a distributor based in York, Pa., that has expanded into

New England and the Southeast, dropped AZEK's PVC decking in 2010 to begin distributing CEVN as well as start selling its own, private-label brand of plastic deck.

How To Shop

"Saying all deckboards are the same is like saying all cars are the same," says Gramlich of TimberTech. "A Chevette isn't a Mercedes."

Though virtually all industry experts agree that composite and PVC decking and trim is far better than it was just a few years ago, they stress that variations between products still run rampant. So how do you tell which product is a peach and which is a lemon? The basic answer from manufacturers is to not accept what companies say at face value and to check closely how they back up their word.

For instance, manufacturers say dealers should press suppliers to give more details about what's in their recipes, such as what percentage of wood flour is in the total mix (over 60% should ring alarm bells), what size wood particles are used (in most cases, the smaller the better), whether the polyethylene used is low- rather than high-density (higher-density polyethylene tends to be stronger, but it's also more expensive, and the sourcing can be spotty), and how much of a filler like talc is used (over 10% may signal cost-cutting).

Fiberon's Ross also urges dealers to ask about the pigment used to color the product. Organic pigments will change over time, while non-reactive pigments are inert and thus will keep a color true for a longer time.

One good way to get a sense of what the manufacturer is doing is to compare its good, better, and best products. Why does the upscale version promise a longer, stronger warranty? It's probably because it has more additives. Knowing how much more, and what extra is in there, can help you decide whether the differences are worth stocking.

Ask manufacturers what percentage of output from the production line is rejected and reground; if it's way below 10%, the company may be intentionally permitting some less-than-optimal products to sneak through to your company's shelves.

Likewise, ask about warranty claims and lawsuits. The volume of claims as a percent of total sales can help indicate the product's performance. At the same time, companies that get sued over a defect are likely to have spent a lot of time making sure that problem doesn't reoccur. How long a company has been in the business also should be taken into account.

Even after making those checks, experts agree that the only real way to be sure of a product's quality is to install a lot of it in a lot of places and then see what happens. Frequently, that's the first time manufacturers discover how builders' embrace of other products can have unintended consequences for their decking and trim.

Pace says he has worried lately about whether paint companies that have made darker colors of heat-reflecting paint have spent any time seeing how that paint affects the expansion and contraction of PVC trim.

Likewise, Bob Simon of Gossen says his company got surprised when its first generation of PVC decking was placed below low-e glass. It turns out that the glass can reflect and focus the sun's rays on a spot near the window.

"We had decks below windows and patio doors that were pretty black–getting scorched," Simon says. "So we discontinued that whole product line, took substantial losses. That's when we decided to change our whole process. ...That's a hard knock we went through, and some are going through that now."

Unexpected problems are a part of the package that comes when you try to sell an ever-evolving product. Understanding how it's made is your first step to reducing that risk.