Best Practices to Prevent Cracks in Composite Deck Boards
Composite decking is a premium, cost-effective solution that’s transforming outdoor living spaces across Australia. Whether you prefer wood-plastic composite (WPC), polyvinyl chloride (PVC), capped composite, or mineral-based composite (MBC), modern decking options closely replicate the natural look of timber—while offering a sleek, durable, and low-maintenance finish that elevates any backyard.
While composite decking is built for longevity, it’s not immune to wear and tear. Factors like improper installation, extreme weather, heavy loads, or structural movement can lead to cracks over time. The good news? These issues are preventable.
In this guide, we’ll explore practical strategies to help you avoid cracking, so you can enjoy a stylish, resilient outdoor area for years to come.
Common Causes of Cracking in Composite Decking
Understanding what causes cracking is the first step to prevention. Here are the most frequent culprits:
1. Thermal Expansion and Contraction
Composite materials naturally expand and contract with temperature changes. Without proper spacing between boards, this movement can create stress and lead to cracking. In cold climates, boards may contract and strain fasteners or the subframe.
Tip: Always follow manufacturer guidelines and use compatible fasteners to allow for thermal movement.
2. Low-Quality Composite Materials
Cheap or uncapped composite decking boards lack protection against moisture, UV damage, and splitting. Premium capped composites, on the other hand, offer superior durability and resistance to environmental stressors.
Tip: Invest in high-quality, branded decking from a reputable supplier and ensure proper installation for long-term peace of mind.
3. Weak or Shifting Framework
If the subframe isn’t properly aligned or reinforced, it can flex under pressure and cause boards to crack. Over time, poorly constructed frameworks may settle, shift, or sag—especially under weight or in extreme weather.
Tip: Choose an experienced installer who uses solid, level, and well-anchored substructures.
4. Heavy Impact or Excessive Load
Although composite decking is built to withstand significant weight, dropping heavy objects or placing concentrated loads on unsupported areas can lead to stress fractures.
Tip: Distribute weight evenly and avoid placing heavy furniture, hot tubs, or gym equipment in unsupported areas.
5. Harsh Weather Conditions
While composite boards perform better than timber in harsh weather, ongoing exposure to sunlight, rain, or freeze-thaw cycles can weaken their structural integrity.
Tip: Clean and maintain your deck regularly to help it withstand extreme weather patterns.
Warning Signs of Composite Deck Cracking
Early detection is key. Watch for the following signs:
- Hairline cracks around fasteners or board edges
- Surface splitting or fissures
- Rough or splintering textures (less common in composites)
- Structural movement beneath the decking
If you spot any of these issues, consult a professional immediately to assess the damage and recommend a solution.
How to Fix and Prevent Composite Decking Cracks
Depending on the severity, your installer may suggest the following:
- Board Replacement: Damaged boards can often be replaced individually.
- Fastener Adjustments: Replacing or repositioning fasteners can prevent further splitting.
- Structural Reinforcement: If the subframe is compromised, joists or posts may need bracing.
DIY repairs without proper knowledge can worsen the issue. Always consult a licensed professional.
Long-Term Strategies to Prevent Cracking
To maintain your deck’s integrity, follow these best practices:
Choose High-Quality Decking
Select composite decking boards with protective capping and a strong internal core. Premium brands offer better resistance to stress, impact, and UV damage.
Hire an Experienced Installer
Professional installers understand proper spacing, fastener compatibility, and subframe requirements to ensure your deck lasts.
Leave Adequate Expansion Gaps
Spacing between boards allows for natural movement, reducing the risk of compression and cracking.
Use the Right Fasteners
Composite decking requires specialist fasteners or clip systems—standard nails or screws won’t offer the same durability or flexibility.
Avoid Overloading
Refrain from placing concentrated weight on unsupported areas. Spread out large items or consider reinforcing areas designed to carry more load.
Clean Regularly
Dirt and debris can trap moisture. Clean your deck every 2–3 months (or at least every six months for low-traffic areas) using warm water, mild detergent, and a soft-bristle brush.
Composite Decking Lifespan & Maintenance
When properly installed and maintained, composite decking can outlast timber by decades. It resists rotting, staining, splintering, and insect damage—making it ideal for Australia’s diverse climate.
However, to maximise its lifespan, you should:
- Monitor for cracks, shifting, or discoloration
- Clean regularly to prevent moisture buildup
- Call a professional for repairs or upgrades
If you’re planning a new build or replacing an ageing deck, a qualified decking installer can help you select the right materials and design for your lifestyle, climate, and budget.
Final Thoughts
Composite decking offers a modern, long-lasting alternative to timber—enhancing the look, feel, and functionality of your outdoor space. While cracking can occur under certain conditions, the right combination of quality materials, expert installation, and ongoing care will prevent damage and extend your deck’s lifespan.
At Ezy Decking, we supply premium composite decking to homeowners across Sydney and Northern NSW. Whether you’re building new or repairing an existing deck, our team is ready to help.
Contact us today to book a consultation and receive a personalised quote from Australia’s trusted decking experts.