9 Composite Decking Mistakes That You Could Be Making


For your deck to withstand extreme climates, it must be made with the right materials. Your deck’s exposure to rugged climates can cause it to wear down over time. Therefore, it’s wise to equip it with hardwearing materials.

According to professional builders, high-quality composite decking is far more heavy-duty than regular wood. When installed correctly, composite timber decking can be the bane of any weather condition. Usually made with the combination of wood fibres and recycled plastic, composite decking is created to survive sub-freezing to extremely humid temperatures.

As promising as it sounds, composite decking requires the correct installation for you to reap its long-wearing benefits. Here are 10 composite decking installation errors that you could be making.

1. Absence of Lag Head Screws

Lag head screws are necessary to avoiding composite decking or any decking for that matter to collapse. Likewise, its absence threatens potential problems with your ledger board attachment. Before installing a new composite decking, diagnose the fasteners of the old one. If your old deck is fastened with nails or screws, it’s best to seek advice from a professional.

2. Wide Gap Between Joists

Building guidelines state that all composite decking must be supported with at least 2”x10” pressure-treated pine joists spaced 30cm apart. This means the gap between your joists shouldn’t be too near or too far. This could mean that additional framing is necessary should you decide to upgrade from your current pressure treated wood deck to a high-quality composite decking material.

3. Weak Deck Frame

Sometimes, too much weight isn’t the reason why composite decking fails. It’s usually because of an incorrectly fasten ledger board. Therefore, the ledger boards should be flashed correctly so water can drain from under the finished wall assembly. Like any timber, avoiding moisture is key to a strong decking frame.

4. Inadequate Ventilation

While composite decking is created to withstand moisture, prolonged exposure to moisture can cause tarnishing of the substructure thus promoting mold growth on your composite decking. Decking boards usually need a 12mm gap from a structure. This avoids capillary action while also allowing water to drain. It’s also important to keep in mind that decking boards should never be allowed to come in contact with another surface unless it’s a substructure. If necessary, you may use ventilation grates to allow airflow.

5. Shallow Deck Footing

Improper installation of concrete footings can cause problems in the future. This can cause havoc on concrete footers during freezing climates if they are not installed below the frost line. The installation of concrete footing at the right depth will allow for better absorption and contraction of the material surrounding it since it freezes and thaws without shifting the deck.

6. Rigid Deck Boards

The temperature of packed boards can be very different from air temperature. This is why it’s wise to let composite decking boards acclimatize before cutting. In order to do this, simply open up the boards and lay them down to let it adjust to the ambient air temperature.

composite decking mistakes

7. Wrong Fascia Installation

The most common malpractice of fascia installation is done by extending the fascia to cover the composite decking board ends. This method invites and traps dirt and moisture in between the gaps of the fascia and the composite decking. As a result, the fascia will warp or pull away from the outer rim joist. Composite decking boards must be installed in a way that they extend past the outer rim joists by less than 2” lengthwise and 1” width wise.

8. Use of Incorrect Clips

The use of non-plastic material or stainless-steel coated clips could cause the deck to erode over time. Composite Decking placed at 400mm or less from the ground must use either plastic or stainless-steel coated clips. This also extends to composite decking having inadequate ventilation. Your boards should be fastened with a 1x clip per joist apart from butt joins or breaker boards.

9. Screw Usage

This may come as a surprise given that screws have been used by professional builders for ages, however, they are not only difficult to work with, they could also be stripping. Technology has allowed advancements in the evolution of screws thus, improving its quality. However, they are still difficult to work with in terms of composite decking installations. As a conclusion, using screws as a fastener for composite decking should be avoided. Even when installed correctly, clips can clutter up an otherwise clean and smooth composite decking panel that’s engineered to look and feel like high-grade wood. As an alternative, you may use a hidden fastener system that creates a clean surface while also providing a solid and stable connection to the deck frame. Clips are attached to the framing boards while the deck is attached to the clips.

While composite decking is made for the purpose of durability, it’s still your responsibility to ensure proper installation and regular maintenance. These methods guarantee that you can reap the benefits of a sturdy, long-lasting, and beautiful composite decking.


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