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How to Fix Cracks in Composite Deck Boards [Step-by-step Guide]

Composite deck boards are a modern marvel for homeowners, blending durability with aesthetic elegance. Composite decking boards are increasingly becoming the go-to choice for homeowners looking for both durability and aesthetic appeal in their outdoor spaces. However, even the sturdiest materials can show signs of wear, such as cracks, which can mar their beauty. What happens when these sturdy boards start showing signs of wear, like unsightly cracks? This all-encompassing guide is designed to unravel the mystery behind these cracks in composite deck boards and composite deck planks and provide practical, easy-to-follow solutions to keep your composite decking boards in tip-top shape.

composite deck boards maintenance

Why Is Your Composite Decking Boards Cracking?

Moisture and Installation

The tale of a composite deck board crack often starts with two culprits: moisture imbalance and installation issues. Imagine installing your brand-new composite decking boards. They appear flawless, but hidden problems may lurk beneath. Inadequate sealing of the moisture-proof layer with waterproof tape is a common oversight that can trigger unilateral expansion of the composite deck planks. This can manifest in several ways:

1. Initially, your deck might look impeccable, but over time, a triangular seam could become noticeable.
2. You might discover a moisture content difference exceeding 2% between the opposite sides of a board.
3. Upon a detailed inspection, it may become evident that the moisture-proof layer’s bonding with waterproof tape is subpar.

This situation highlights the importance of meticulous installation and attention to detail, ensuring that each board is correctly sealed and protected against moisture.

Humidity: The Invisible Foe

The impact of humidity on composite deck boards is often underestimated. Leaving a deck area unoccupied for extended periods, especially without regulating humidity levels, can lead to the composite decking boards shrinking. This shrinkage can cause cracks or even make the boards bow, significantly affecting the aesthetic and structural integrity of the deck. It’s a clear indicator of the necessity for consistent humidity control in areas where composite decking boards are installed.

Fix Cracks in Composite Deck Boards

Installation Precision and Humidity Harmony

One of the primary causes of cracks in composite deck boards is uneven pressure during installation. This problem can be prevented by ensuring a balanced and secure installation process. If you’re planning to leave your space unoccupied for a while, consider simple measures like placing a basin of water indoors. This can help maintain optimal humidity levels, reducing the likelihood of your composite decking boards shrinking and cracking.

Creative Solutions for Gap Management

For larger gaps, glass glue can be an effective solution, providing a strong and durable fix. For smaller gaps, typically less than 5mm, bakelite powder is recommended. A creative and effective approach involves mixing water-based transparent putty with sawdust. This not only fills the gaps efficiently but also maintains the natural look and feel of your composite decking boards. For those who enjoy a bit of DIY, using a thin wooden strip followed by the putty-sawdust mixture can offer a seamless repair solution.

01.25 environmental factors affecting behavior of WPC decking

If you’re unsure about the right materials for the job, a visit to a local hardware store for a wood floor joint filler can provide you with the right product. These filters are designed specifically for such repairs and should be an essential part of your deck maintenance toolkit.

Seasonal Care for Lasting Beauty

Interestingly, larger cracks in composite decking boards are not necessarily a cause for alarm. During the warmer months, these boards tend to expand, allowing larger gaps to fit without deforming the floor. In contrast, during colder periods, maintaining a semi-dry condition with a rag can help reduce the size of these gaps. A pro tip for year-round care is to use solid wax during the summer and maintain it through the winter, preventing the re-emergence of large gaps.


Composite deck boards are a significant investment in the aesthetic and functional appeal of your home. Understanding the causes of cracks and implementing these effective treatment methods ensures that your composite deck planks remain a beautiful and integral part of your living space. Regular maintenance, combined with careful installation, is the key to preserving the longevity and beauty of your composite decking boards. By following these guidelines, you can enjoy a stunning, crack-free deck that stands the test of time. 

 Oakio composite deck boards

Oakio composite deck boards, celebrated for their durability and style, require proper care to maintain their pristine condition. In case of cracks, clean the area and use a composite deck filler designed for Oakio boards, ensuring a perfect color and texture match. For larger damages, replacing the affected section following Oakio’s guidelines is recommended. Regular maintenance and prompt repairs will not only preserve the aesthetic appeal of your Oakio decking but also extend its lifespan, allowing you to enjoy your living space to the fullest.

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