So, you’re planning to upgrade your outdoor space and thinking of going with composite decking? Great choice! It’s low-maintenance, eco-friendly, and looks absolutely stunning. But here’s the truth—not installing it the right way can create big headaches later.
In this blog, we’ll cover the top 5 mistakes people make while installing composite decking in Australia—and how you can avoid them like a pro. Whether you’re a DIY enthusiast or hiring a tradie, this guide will help you get the best results from your deck.
Poor Subframe Planning and Support
Let’s start from the ground up. One of the biggest blunders is not planning the subframe properly.
What goes wrong:
- Using timber that’s not treated for outdoor use
- Wrong joist spacing (either too far or too close)
- No allowance for water runoff or ventilation
In Australia’s tough climate—with hot summers and rainy winters—your deck needs strong support. If your frame isn’t solid, even the best decking boards will warp or sag over time.
🛠 Quick Tip: Always use H3 or H4 treated pine or even aluminium frames. For composite decking, the ideal joist spacing is 300–400mm depending on board thickness.
Ignoring Manufacturer Guidelines
We know how tempting it is to just “figure it out” on the go. But each composite brand has different installation requirements. If you don’t follow the instructions, you may lose warranty coverage—and that’s not something you want!
What people often miss:
- Using the wrong screws or clips
- Not allowing correct spacing between ends
- Mixing products from different brands
According to one of the leading composite decking suppliers in Australia, nearly 40% of customer complaints come from improper installation.
📄 Always read the installation manual or ask your supplier for guidance.
Inadequate Ventilation and Drainage
Composite decking is water-resistant, but not waterproof. If moisture gets trapped below the deck, it can cause mould, discolouration, and even damage to the subframe.
What you should do:
- Keep at least 50mm of airflow space under the deck
- Avoid placing boards directly on concrete or soil
- Install drainage channels if needed
🌀 In humid areas like Queensland or coastal NSW, good ventilation becomes even more important. Make sure your deck can breathe!
Incorrect Board Gapping
One common misconception is that composite decking doesn’t move. But that’s not true—it expands and contracts with temperature changes. That’s why spacing is key.
Common issues:
- No gap between boards = boards may buckle in summer
- Gaps too wide = dirt and leaves get stuck, looks untidy
📏 Best practice: Leave a 5–7mm space between boards and 1–2mm from the edge of walls or posts. Use spacers or concealed clips offered by your decking supplier.
This small detail makes a huge difference in the long run.
Poor Planning of Deck Layout and Aesthetics
Some people get so focused on installing the boards that they forget to plan the layout visually. You want your deck to not only last but also look amazing.
Mistakes to avoid:
- Not staggering the boards (like bricks)
- Long, continuous board runs without breaks
- Forgetting picture framing or edge trims
🖼 Think of your deck as an outdoor room. A little extra planning on design goes a long way—especially when you invite guests over for that weekend barbie!
Bonus Tips for First-Time Installers
Here are a few extra tips that’ll make your composite decking project even better:
- Pre-drill when fixing near the ends to prevent cracking
- Use chalk lines to keep boards straight
- Keep extra boards for future repairs or extensions
🛒 And of course, make sure you buy composite decking from a trusted local supplier. That way, you get the right advice, after-sales support, and product warranty—all without long delivery delays.
Where to Buy Composite Decking in Australia
When you’re ready to start your project, make sure you’re dealing with reliable composite decking suppliers who know the local conditions and offer high-quality boards.
👉 We recommend checking out SND Trade – we offer a wide range of premium composite decking, fast delivery across Australia, and expert advice for homeowners and builders.
Final Thoughts
Composite decking is a smart investment—but only when installed correctly. By avoiding the mistakes we’ve listed above, you can enjoy a long-lasting, low-maintenance deck that looks beautiful and performs well all year round.