Top 10 Reasons Why Composite Decking Is a Bad Idea for Boardwalks

After the destruction of so many miles of boardwalk by hurricane Sandy, new construction bids and RFQs are on everyone’s minds.  Unfortunately, pressure is being brought to bear on city planners from environmental lobby groups to use composite decking to rebuild the boardwalks.  I’m not going to try and pretend I’m unbiased in this ongoing fight between tropical decking and composite decking.  Working for a lumber company, I obviously have already firmly announced my opinions on which is the better product.  But I hope to be able to lay out some serious concerns about using a composite decking product (regardless of manufacturer) in a boardwalk application.  In the end, I think you will see that the best choice is natural wood, probably something like Cumaru or Ipe.

Mediocre Hardness

Ipe and Cumaru decking are almost 10 times harder than composite products.  While this medium hardness may be fine for your backyard where a couple people walk across it daily, imagine the damage wrought by hundreds of thousands of people walking across a boardwalk each day.  As we will see in the points below, damaging the outer core of composite decking can be catastrophic, and this lower hardness practically ensures that damage will occur in such high traffic conditions.

Composite heat build up

Image courtesy of FamilyHandyman.com

Heat Build up

Composite Decking is essentially plastic.  Some manufacturers use an outer shell of pure polyethylene (the same stuff used in water bottles), while others blend the plastic in with the wood flour (ground up wood product).  Plastic is notorious for retaining heat and getting very hot in direct sunlight.  Again, while this may be fine in your shaded or partially shaded backyard, a seaside boardwalk is in direct sunlight all day long.  I wouldn’t recommend walking barefoot on any boardwalk for many reasons, but it happens.  At least once anyway.  Once you burn your feet, you probably won’t do it again. 

In addition to the discomfort factor, when plastic heats up, it breaks down.  Some variants will exude their oils, some will let off gas byproducts, but all of them will weaken over time.  Suddenly your boardwalk is very hot, and it smells like… well, burned plastic. 

Plastic also retains its heat longer, and even after the sun goes down, the boardwalk will still be hot, and that plastic will continue to break down.  This constant bombardment day in and day out will result in a boardwalk that needs to be replaced rather quickly.

Slippery

What is plastic?  It is an oil based product.  Oil and water do not mix, and when this is attempted, you get a very slippery surface.  Most composite manufacturers have attempted to fix this by adding texture and faux wood grain, and in many cases, they have had some success.  But look at your average boardwalk.  As stated above, the heat build up will degrade the plastic and even cause it to weep oil.  The boardwalk is by the ocean, so it is constantly exposed to water.  Now add in ketchup, mustard, cotton candy, funnel cake, deep fryer oil, suntan lotion, surf wax, and all other manner of stuff that will inevitably be spilled or dropped onto the plastic surface.  Imagine the army of lawyers ready to represent the tourist who slips and falls on your city’s boardwalk.

Non-Biodegradable

While we are on the topic of replacing the boardwalk, what happens to this composite lumber when it is torn up and carted off?  Composite manufacturers and environmental groups tout the “green” nature of composite decking, yet the one place where this material will be guaranteed to last a lifetime is in the landfills. 

Secondly, and even more importantly, is what will happen when another storm hits the boardwalk and washes this non degrading material out into the ocean?  God forbid another storm like Sandy hits, but I’m sorry to say that it will happen one day.  Unless the normal weather patterns shift significantly (and we are in real trouble if that happens), the east coast of the US will always be hurricane alley.  We can count on storm damage washing boardwalks or parts of them out to sea, where those non degrading pieces will sink to the bottom and remain there for thousands of years, or wash ashore somewhere else and be moved to a landfill where those pieces will sit for thousands of years.  Even the most hardy of exterior woods like Ipe, however, will degrade completely in a landfill or in the ocean in about 10 years.

Molding Composite Decking

Mold growth on composite decking

Not Weather and Mold Resistant

This may be the most shocking element of composite decking that people don’t usually realize.  The original composites were homogenous mixes of wood flour and polyethylene or PVC extruded into boards.  These quickly fell out of favor (mostly due to class action lawsuits), because wood flour is still wood, and it will absorb moisture very quickly despite the plastic binders. 

Real wood contains complex structures that absorb and shed water and nutrients that feed the tree. Natural resins protect against insects and mold.  Wood flour is basically wood ground very fine, thus eliminating all the natural resins and cellular structure that defeats insects and mold.  The cellulose that is left over in wood flour is like candy to mold, since it is already broken down into simple sugar form. 

Later “advancements” encased this wood flour core with pure plastic “cap stock,” thus blocking out all these harmful factors from the vulnerable inner core.  This, however, produces a bigger issue now that there is a heterogeneous construction that reacts differently to heating and cooling and daily wear and tear.  This process can crack the shell or cause it to separate from the core, thus compromising the strength and weather resistance.  If the thin cap stock is punctured, the inner core is exposed to the elements where mold and decay can take hold.  Just the act of installing the decking will puncture this, as the boards are screwed down or cut to length exposing the core.

Not Scratch Resistant

Some of this relates back to the medium hardness, but essentially, polyethylene is a weak plastic; polypropylene, though rarely used, is much tougher. Regardless of the type of plastic being used, the cap stock style decking relies upon this water resistant outer shell to weather and mold proof the inner wood flour core.  However, like cheaply made plywood, this shell is extremely thin and easily scratched, thus exposing the water and mold loving inner core. 

Most composite manufacturers, in fact, warn you not to use a metal snow shovel to clear the deck.  In a larger boardwalk situation where the city plows the boardwalk just like they would the roads, you can imagine what damage a truck plow would do to it.  Even if an army of city workers armed with snow shovels is used, are they really only going to use plastic shovels in a wet and icy environment?

petrochemical plantNot Renewable

Polyethylene, polypropylene, and poly vinyl chloride do not grow on trees.  These are petroleum products that rely upon one of the most environmentally unfriendly industries around.  The entire composite decking industry was actually started by the Oil companies who were mandated to find a use for the massive amount of harmful byproducts produced in their manufacturing process.  So while at least this waste is being put to use, it is still reliant upon heavy industry to produce it in the first place.  Most composite manufacturers claim a certain percentage of recycled products, and I have no doubt this is true.  As I have shown above, we are still talking about a non degradable material that will need to be replaced and eventually end up in a land fill.  How is that green? 

Ipe, Cumaru, Redwood, etc does grow on trees, however.  The myths of the lumber industry deforestation are just not true, and heavy regulation and forestry management is planting 10-20 trees per each one cut down.  These grow back and are constantly renewable, let alone the key role that trees plays in our environment.  The entire lumber industry makes up about 2-3% of deforestation in reality.  How many oil companies do you know of that put oil back into the ground?

Not Fire Rated

Ipe has a class A fire rating which makes it very difficult to burn.  Composite decking does not, and in fact, when the plastic melts, it releases very toxic gases.  In the backyard, where you might occasionally drop a charcoal briquet, this doesn’t sound like a big deal.  Now look at a boardwalk where hundreds of restaurants and street vendors work with open flames, grills, burners, deep fryers, etc.  Imagine the catastrophe when a fire breaks out, and the decking begins to melt.  Even if it isn’t a total loss, some boards will deform from the heat and need to be replaced.  The removed boards then have to be disposed of, and we go back to the environmental issues mentioned above.

Not as Strong

Strength of the composite materials will vary from manufacture to manufacture, but the fine print of most installation manuals will recommend you install the decking boards on 12″ on center joists. The typical 16″ center can be done, but bounce and deformation is more likely.  Most plastic has a “memory” too, and once it is deformed, it won’t spring back.  The wood flour core is not very strong and relies upon the outer plastic shell to stiffen it.  If this shell is compromised in any way, the strength will fall off considerably.  Now, release the summertime throng of traffic on the boardwalk and imagine how that bounce and deformation quotient will climb exponentially.  So you install the composite on 12″ centers.  Imagine the additional cost of the structure over the entire span of an average beach community boardwalk!

Unpredictable Movement

While we are on the subject of deformation of the boards, let’s look at movement.  Composite decking manufacturers tout how stable their products are and how superior they are to wood because of this.  Wood moves, we all know that.  But we also know how and why it moves.  Wood will move across the grain and almost not at all along the grain.  We can even predict how much it will move, and we have hundreds of years of experience building around that movement. 

Plastic, however, also moves, and it moves in a big way when heated as stated above.  The inner wood flour core also moves, because it is wood.  However, without the structure of natural wood, there is no grain, so it will expand across and along the boards.  Add the plastic outer shell, and now it only expands.  That plastic shell is stretched as the core moves, but it won’t snap back as the wood flour shrinks again.  Now you have a core that can separate from the shell, and you have uneven warping along the length of the board, especially since the ends that were sawn to length have exposed cores that will swell even more than the interiors. 

Boardwalks are wide structures, and end to end butt joints have to happen to span the entire width.  Now you have swelling on both ends of the boardwalk as well as each of those joints in the middle.  If the boards are staggered, as is common in construction, you end up with swelling and moisture and mold traps spaced sporadically all over your boardwalk.  This sounds like a recipe for disaster that will need to be replaced quickly, thus sending all this composite material into the landfill.  See points 3 and 6 above.

Got that sick feeling in your stomach yet?

ipe boardwalk

Ipe boardwalk at Disney World

I’ll be honest, when I started outlining this article I came up with 20 points within 10 minutes.  I’m not even mentioning the aesthetic reasons for not using composites.  Who has nostalgic childhood memories of strolling along the plastic boardwalk?  I didn’t even mention the price either.  In every case you will find that composites are equal to or more expensive than Ipe, which is considered to be the most expensive decking option on the market.

I think price and aesthetics are important, but let’s get real: the probability that this boardwalk will need to be replaced within 5 years, if by no other reason than storm damage, leads to the environmental impact.  I hear about the green nature of composite decking all the time.  The funny thing is that none of the manufacturers are calling it a green product anymore.  20 years ago it was the call to arms, but lawsuit after lawsuit has changed their tune.

So City Planers and contractors, the next time you are approached by the Sierra Club or Greenpeace, and they threaten to put an injunction against you if you use natural wood, ask them how they can in good conscience support a composite product that isn’t renewable, relies on non-green industries to produce waste, and will not biodegrade.

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9 Responses to “Top 10 Reasons Why Composite Decking Is a Bad Idea for Boardwalks”

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  1. Your article is great as far as it goes, but now you need to sell them on FSC. FSC IS NOT GREENWASH! FSC has worked to achieve a high level of credibility. I know it’s not the only cert organization, but if you read the studies you’ll see it’s without question the one with the strongest procedures and cred. Sell them on FSC product, then let FSC help you make your case.

    • Shannon Rogers says:

      Have you tried to procure any sizable amount of FSC Ipe Stephen? It is next to impossible to provide more than a few decks worth before the material becomes very scarce very fast. Next you have little control over the grade and dimensions. The thing is that Ipe doesn’t have to be certified to be an environmentally responsible product. The long term forestry plans REQUIRED in Brazil go a long way to ensuring the sustainability. I’ll respectfully disagree that FSC has the strongest procedures based upon our extensive experience working with FSC material and trying to trace that material back to the source for Lacey and CITES purposes. The reality is that just because a product is labelled FSC doesn’t mean it is “green” and responsibly harvested. Check out our other article on this topic, http://www.mcilvain.com/fsc-alternatives/

  2. I’ll cite http://www.ecologyandsociety.org/vol16/iss1/art3/
    I can’t seem to find the more detailed paper I read, so this one will have to suffice.
    The real issue is whether you want to fight environmentalists or find ground where you can agree.
    If the latter, my suggestion is that you accept that, for the moment, FSC is the gold standard.
    At least SOME of the other third party certifiers ARE greenwash, in my opinion.

    • Shannon Rogers says:

      Stephen,
      I remember reading that document and I’m glad you were able to dig it up. If you find the other paper you were looking for please share that too. You bring up a good point about finding common ground and I think that is good advice. Environmental issues aside, I have a hard time pitching something to my customers that I know full well I won’t be able to supply in any quantities. Time and again, firms that spec FSC Ipe are disappointed with what they are able to get and have to change the spec just to get the job completed. The truly sad part is the amount of FSC material (not just Ipe) that gets labelled as such and was never FSC to begin with just so that an order can be filled under the gun. It makes one wonder how valuable the brand is when the material in question can’t truly be verified.

  3. David Prior says:

    I don’t like the idea of cutting tropical hardwoods. What’s wrong with eastern cedar? There is large quantities in the Maritimes,especially New Brunswick. Another great North American wood is hackmatack (aka tamarack or juniper). Tough,very strong, rot-proof and underutilized. Very abundan in eastern Canada and most likely Maine and Vermont.

    “Hackmatack is the preferred species for boat knees because of its slow even growth, … Hackmatack is prolific in the swamps and bogs of south-west Nova Scotia. … growth, which can be advantageously used for sawn frames and deck beams.”

    http://www.amoswood.ca/12-yellow-poplar-flooring.html#

    • Shannon Rogers says:

      David, thanks for speaking up and presenting some alternatives. The problem I see with Eastern Cedar is a durability issue for a commercial application like a boardwalk. It’s lower hardness rating and lower density would pose some serious problems several years down the road. Many of the east coast boardwalks began their quest for new material because of the worn down nature of the softwoods they chose before. Tamarack is an interesting option that I admit I had not considered. Certainly with a hardness on par with Cherry or Walnut it will stand up to more foot traffic but I still question if that will cut it with such a high use operation. How available it is? I haven’t researched it enough to know if it can be sourced in the extremely large quantities needed to fill the shoes of Ipe’s place in the market.

      Finally, why don’t you like the idea of cutting tropical hardwoods? If we don’t support that industry then those forests lose value and will be sold off for industries that can make use of them like cattle ranches (the number 1 cause of deforestation). I don’t deny that irresponsible forestry is happening, but it is becoming much less rampant with government regulation down there and of course US Lacey Act watching over everything here. I realize I’m biased, but I firmly believe that buying tropical hardwoods is actually a green action. We are the ones who take the best care of those forests.

      Thanks again for the comment and the food for thought on Tamarack. I’d love to learn more about it.

  4. Robert Kincaid says:

    Great article on the down side of the componsit materials compared to the real wood. I being a long term lumber guy dislike any subsitute of the real thing. I also do not see the benefits of FSC in the real world, but the politics of our markets mandate us to label our products in a manner that consumers believe we are serous about being good land stewards. THe International Hardwood Product Association has a solid position about using the tropical forests and should be a good topic of conversation. I posted a blog to the International Wood LinkenIn world about Mayor Blumbergs bad decision to use concrete instead of wood. It is amazing that the environmentalists have been able to persuade the govenment hacks of altenatives to wood being more friendly choices. Steel studs, concrete and composits have their place, but my vote is with the standard sustainable and renewable resource, hardwood. Have you considered plantation teak versus Ipe? Also the thermo treated wood is another choice for weather resistant material. I also recommend cypress when the traffic is lower like a back yard decking. Thanks for the time taken to write and educate your readers

    • Shannon Rogers says:

      Thanks for the comment Robert. I must admit that the composite stuff has come a long way and they are making strides to improve the product. The mold, fading, and cracking horror stories have taught those manufacturers a lot and the product has improved to the point where it makes a passable decking option for residential applications. Some of the pure PVC products for trim and siding have also come a long way and make a good option for exterior projects. Like you, I’m a wood guy so it is tough for me to say that. As a commercial solution however, I cannot get behind composite decking. From an environmental standpoint, I have an even tougher time supporting a product that relies upon harmful industrial waste for its raw material to make a product that isn’t biodegradable.

      Regarding Plantation Teak, it is a market we have investigated since we are also one of the largest importers of genuine Teak. Right now, the Plantation Teak on the market is too inconsistent and actually doesn’t have the same weather resistance that Teak is known for due to a much lower silica content and a much higher percentage of knots. While appearance means little in the performance of the material this has posed a big problem too because the market wants clear material with good color consistency. People have an impression of what a Teak deck should look like and the plantation stuff doesn’t live up to it yet it is still a very expensive wood.

  5. Sergio Roda says:

    It is impossible to FSC a tropical forest!!! You can FSC Pine – Oak – Eucalyptus because they grow close together but in tropical forest the trees are far apart sometimes miles apart. In Brazil we have responsible wood companies that cut only government approved trees but unfortunately we have here also dishonest wood companies that lie about their wood sources

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