As we already discussed in a previous article, wood decking is more durable than composite decking (see Parts 1, 2, 3 & 4). This durability is one of the reasons why wood decking is a more environmentally friendly option than composite decking.
Wood Decking is Stronger than Composite Decking
Composite decking manufacturers typically recommend that their boards be installed on 12” center joists rather than the 16” center joists you would typically use for wood decking boards. If you use the 16” center joists you may notice warping and deformity. Because of the high amount of plastic-based content in composite decking, once it becomes deformed it simply won’t bounce back into place. As soon as that deformity takes place in the hard plastic shell, a composite decking board becomes significantly weaker than a wood decking board. This relative board weakness may not make much difference for a low-traffic residential deck, but for a high-traffic city boardwalk, it will most likely become deformed and need to be replaced after a few short years. So you either have to install the 12” joists or all those boards will quickly end up in a landfill.
Composite Decking Moves Sporadically While Wood Decking Moves Predictably
One of the major selling points for composite decking is its supposed stability compared to wood decking. Because wood is an organic product, it will move over time. This doesn’t have to be a problem, because the movement of wood is predictable. Both the direction and the amount of movement we see in different wood species can be predicted with a high degree of accuracy. This is because people have been building all sorts of different structures with wood for thousands of years.
What composite manufacturers may not mention is that their products also move. Composite decking moves when the temperatures heat up and the plastic shell begins to weep oil and melt. The core that is made up partially of wood flour also tends to move. Unlike natural wood boards, however, there’s no telling which direction or how much the composite boards will move. There’s no grain pattern for the boards to follow. As the core expands, the outer plastic shell is stretched. Unlike natural wood, however, that shell won’t shrink back into place as the weather changes. It will remain stretched. When the inner wood flour core shrinks, there can be a separation that forms between the shell and the core. Now consider all the places where the boards are punctured by screws or the edges of these boards that are sawn off. All of these sections of the exposed inner core will be impacted by the elements, leading to a large amount of warping and deformity.
Imagine all of the instances of trapped mold, moisture, and swollen boards you’ll end up with if you construct a boardwalk out of composite decking boards. Any place where you see butt joints close together you’ll likely see this kind of warping. The result will be a damaged, uneven surface that will quickly become unusable. Once again, these non-biodegradable boards will end up as garbage that will sit around possibly for centuries. That doesn’t sound like a very green option!
As you can see, there are a whole host of different reasons why wood decking is a superior choice for boardwalks. It’s more aesthetically pleasing, more user-friendly, more durable, and better for the environment. Not to mention that it tends to be more affordable than composite decking. So if you’re on a city planning board that’s considering boardwalk material options, keep these reasons in mind when you make your decision.