Even while tropical decking is generally preferable over composite decking, the effects of picking a subpar product are amplified when you’re creating a large public structure like a boardwalk. In Part 1, we discussed the four main issues with using composite decking materials to construct boardwalks: lower hardness rating, heat retention, slippery surface, and unpredictable movement. Despite how important such problems may seem, they are only the beginning of the potential issues when building with composite decking!
Although the strength of composite materials varies, almost all manufacturers recommend putting their decking boards on 12″ center joists, according to their installation manuals. The more typical spacing of 16″ for boardwalks is probably going to result initially in bounce and then in distortion later. Additionally, the problem of bounce is more serious with composite materials since once plastic is bent, it cannot be restored to its original shape. The exterior plastic shell plays a major supporting role, because the wood flour center is not at all sturdy. The strength of the entire board is put at risk if that plastic shell is weakened. Bounce and distortion are inevitable on a boardwalk throughout the summer because of the heavy foot traffic. However, it is obvious that putting boards on 12-inch centers instead would significantly increase the expense of any project, and especially that of a large public boardwalk along the shore.
Poor Resistance to Mold & Moisture
Did you realize that contemporary composite decking isn’t actually weather- or mold-resistant? Quite different from today’s composite decking goods were the first composite decking boards to hit the market. They were initially made of a mixture of PVC or polyethylene and wood flour, but that construction was immediately abandoned since wood fibers, even when bonded with plastic, can easily and quickly absorb moisture.
Of course, genuine wood can also do that, but it does so in a predictable way because of the natural structures found throughout the logs. Real wood also contains resins that guard the wood from insects and mold. On the other hand, such organic structures and resins are removed by the manufacturing of wood flour which is used in making composite decking. The resulting wood dust contains broken-down cellulose structures that mold may readily consume.
Today’s composite decking now encases a wood flour core in plastic “cap stock,” intended to keep out moisture from the readily damaged core, to delay or decrease this eventual breakdown of the wood flour. However, despite what the creators intended, the situation is even more hopeless than with the previous versions of composite decking. Now, the inner core is exposed to the elements whenever the cap stock is punctured, which can happen even during installation. In addition to easily affecting the board, mold and decay can also result in the shell of the board cracking or separating from the core, which further reduces the board’s strength and weather resistance.
Continue reading with Part 3.
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