Waterproof Composite Decking Material Creates a Long-Lasting Deck in Any Climate

Waterproof composite decking material after a rain.

Using waterproof composite decking material helps avoid mold and mildew problems in wet climates.

Growing up along the Florida coast, I had several friends who complained about the heat, humidity, thunderous summer rainstorms, and the endless bugs. One of my friends decided she’d had enough of the weirdest state in the south, and left the sun-drenched swamps of Florida for the merely drenched hills of Portland, where she escaped the heat and the bugs but not the humidity or the odd notions.

Even without Florida’s heat and bugs, she discovered that water is a destructive force all on its own. The wooden deck that came with her house swiftly succumbed to mold and mildew, becoming a slimy mess. Rotting wood doesn’t make for barefoot-friendly decking, so my friend reacted the way most homeowners do and simply stopped using the deck. Eventually, this led to something worse: structural damage as the boards warped, cupped, and eventually rotted away. Now she needs to replace her deck and is looking into waterproof composite decking material. Rigorous maintenance schedules aren’t my friend’s biggest strength, and one of the advantages of composites is that they require far less maintenance than wood, especially in humid climates. Even if you live in a drier state than Oregon or Florida, there are still plenty of reasons to seek out decking that’s designed to resist moisture. Hot tubs and swimming pools, for example, can be just as brutally destructive to wooden decks as the climate, and sometimes even more so due to the chlorine and other chemicals involved.

How Water Damages Wood

Wood is comprised of tissues that transport water up and down the length of a tree. Even after the tree has been cut down and its trunk sawn into boards, these fibers continue to store water. In fact, this moisture content plays a role in the dimensions of a piece of cut lumber. A dimensionally stable wood board is about 20% moisture content. The problem arises when the moisture content rises above roughly 30% of the weight of the board. At this point, the water is no longer within the fibers of the board but is between them. The effect is twofold; first, the water begins separating the fibers. A freeze can speed this process along when water trapped between fibers expands. Next, this free water creates the necessary conditions for fungi and microbial life that feed on wood to grow. There’s a feedback loop to these factors, since separated wood fibers allow more water to intrude, and microbes enrich the environment by eating the wood, encouraging more organisms to move in.

Of course, there are ways of preventing this, and you don’t have to watch helplessly as your deck crumbles away. The most common method of a preserving a wood deck is to seal the wood surface with a coat of polyurethane sealer shortly after it’s installed. This is a fairly effective way of preserving a deck, but it isn’t totally foolproof. It’s a very rare wooden deck that has the underside sealed against the elements, for instance, yet moisture will rise from the ground and condense on the underside of the boards. Sealant also needs to be applied roughly every two years or it stops being an effective preventative measure. This is something that my friend–and honestly most homeowners–are unlikely to remember to do, especially on a consistent schedule. This means that in the saturated climate of the Pacific Northwest or in other humid areas of the country, decking that is built to be waterproof from the outset will make for a longer lasting, lower maintenance, and better-looking deck for your home.

What to Look for in Quality Waterproof Composite Decking Materials

Composite decking is a blend of synthetic and natural materials. The first generation was made of shredded plastic bottles and sawdust melted together and extruded as a board. Although non-permeable plastic was a large part of the mix, these weren’t waterproof boards. Water could intrude between the wood fibers and plastic components separating them. It would be followed by fungus and mold, and eventually these early composite boards would come apart. This generation of boards also had a reputation for being slippery when they got wet, which is a drawback in climates where it is frequently raining.

The solution was a waterproof cap on the surface of the board. This protected the core of the board from water intrusion, and helped it to last longer. The cap was a step in the right direction, but could still suffer some problems. Since these caps only covered the upper surface of the board, water could still intrude from the underside. When nails and screws were driven through a board, it would penetrate the waterproof cap and create a path for water to get to the core of the board. Some manufacturers have taken steps to address these issues, and homeowners looking for truly waterproof composite decking material should look for composite boards with the following features:

  • Full capping surrounding the board with a layer of waterproof material for a fully protected core above and below. Outside of moisture resistance, another key thing to look for in the capping material is that it provides a non-slip surface that gives traction when the board is wet.
  • Co-extruded capping is extruded along with the board as it leaves the mold, ensuring that the capping and the core form a single unit. This is another key step in ensuring a composite board remains waterproof over the long-term, since capping that isn’t bonded to the core of the board can peel or crack, leaving the board vulnerable to water intrusion.
  • Hidden fasteners are clips that insert into a groove in the side of the board and are screwed into the substructure of the deck. This means no screws pierce the board itself, keeping the board’s capping intact so it can better resist moisture. Decking that uses hidden fasteners also has a smooth, streamlined look and feel, with no screw heads to worry about.

The purely cosmetic advantage of the capping on composite decking is that it makes these boards look a lot better than uncapped boards. The rubbery cap can more easily be made in a variety of rich colors than the core of the board can, and the cap is colored all the way through, meaning that scratches won’t reveal a different color underneath (which is the case with stained wood). Capped boards also have a much more natural, less ‘plastic-y’ look and feel than uncapped ones, which gives your deck the appearance of real wood.

One outstanding composite decking material that offers coextruded, fully-capped boards is Infinity from Fortress Deck. Infinity is a high-quality composite that’s waterproof and will stand up against rain, snow, and water from every direction. With its realistic wood grain and hidden fasteners, it stands out beautifully even as it stands up to the elements. If you’re in need of low maintenance waterproof decking, contact Fortress to find out more, and take a look at Fortress’ other high-quality products if you have more home projects underway.

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