Does Composite Decking Expand And Contract?

  • Home
  • Decking

Composite decking has surged in popularity in the recent past, offering a low-maintenance, sustainable, and highly durable alternative to traditional wood decking.

Composed of recycled wood and plastic fibres, this combination gives composite decking some unique characteristics, including its resistance to pests and decay. But with these benefits, one question that often arises is: does composite decking expand and contract?

Understanding the concept of expansion and contraction in composite decking is critical to its longevity and performance. Like many materials, composite decking is subjected to changes in size due to temperature fluctuations and humidity levels.

These shifts can lead to gaps, buckling, or warping if not appropriately accounted for during installation.

The Science Behind Expansion and Contract

Expansion and contraction in materials is a fundamental scientific concept. When subjected to changes in temperature, most materials will expand (increase in size) or contract (decrease in size). This is due to the kinetic energy that causes the molecules to move faster (expand) or slower (contract).

Temperature and humidity play crucial roles in the expansion and contraction process. Warmer temperatures energize molecules, causing materials to expand, while colder temperatures have the opposite effect. High humidity levels can also cause materials to absorb moisture and expand.

In composite material, this phenomenon, known as thermal expansion, is a key factor to consider. When the decking absorbs heat, it expands, and when it cools down, it contracts. This continuous process can affect the overall performance and durability of the decking if not properly managed.

Composite Decking vs. Wood Decking

When it comes to expansion and contraction, there are distinct differences between composite and wood decking.

Wood decking is highly sensitive to moisture and temperature changes, causing it to expand and contract significantly. It’s not uncommon for wood decks to warp or split due to these changes, particularly if they’re not treated or maintained properly.

Composite decking, on the other hand, has been designed to mitigate these issues. While it still experiences some degree of expansion and contraction, the amount is typically less than wood decking. The plastic content in composite decking makes it more resistant to moisture, reducing the impact of humidity on its size changes.

However, the fact that composite decking does still expand and contract underlines the importance of proper installation.

Accounting for these movements during the installation process can help avoid potential damage, ensuring the longevity of your decking and maintaining its aesthetic appeal. Read our blog post for valuable decking maintenance tips!


Composite Decking vs. Wood Decking

Factors Influencing Expansion and Contraction in Composite Decking

Sure, you’re thinking about getting a smashing composite deck, but have you considered the factors that could cause it to expand and contract? First off, the seesaw of temperatures we often experience here in the UK can cause your decking to bob between expanding and shrinking.

And what about the colour of your deck? Darker shades might look sleek and modern, but they do tend to soak up more of that glorious sunshine, resulting in a touch more expansion. On the flip side, a paler colour might keep the expansion in check, but you’ll have to juggle this with your design goals.

Lastly, where you’re planning to put your deck can have an impact. A sun-trap garden might mean more expansion, while a coastal spot could face its own challenges with sea air and humidity. As always, it’s about weighing up the pros and cons.

How Much Does Composite Decking Expand and Contract?

So, you’re likely wondering, “Just how much does composite decking expand and contract?” Well, let’s try to answer that question.

The degree to which composite decking expands and contracts can depend on several factors. But let’s get a bit of perspective first. Compared to traditional wood decking, composite decking is a champion when it comes to stability.

The fact that it’s a blend of wood fibres and recycled plastics means it’s less prone to the dramatic size changes often associated with pure timber.

Generally speaking, composite decking boards can expand and contract along their length by as much as 1-2mm per metre over a 10-degree Celsius fluctuation in temperature. However, this can vary depending on the quality and specific type of decking.

Nevertheless, Most experts are of the opinion that composite is probably among the best materials for decking.

High-quality composite decking, for instance, is specifically engineered to resist significant expansion and contraction. These boards are designed with ‘grooves’ that enable them to handle temperature fluctuations better than cheaper alternatives.

You could say they’ve got a bit of give, which allows them to roll with the punches when it comes to changes in the weather. Certain colours and finishes of composite decking can also impact the rate of expansion and contraction.

Darker boards, for example, can absorb more heat and therefore may expand more than lighter-coloured boards.

Let’s not forget, location plays a role too. A deck basking in the sun all day long will naturally experience more temperature variation than one tucked away in a shaded corner. Consequently, it might see a bit more expansion and contraction action.

So, while composite decking does indeed expand and contract, it’s generally a far cry from the drama that can unfold with traditional timber decks.

Proper installation techniques, like allowing for appropriate gaps between boards, can ensure your deck stays shipshape through sizzling summers and frosty winters alike.


How Much Does Composite Decking Expand and Contract

Planning and Installation Considerations

Now, let’s talk about installing your deck. It’s not just about making it look fab – you need to consider the practical side, too.

Spacing is key here, whether it’s between the boards or between the deck and any solid objects. You’ll want to leave a gap of around 10mm or so to allow for that expansion and contraction.

Another thing to remember is your joist spacing. While around 400mm centres is a good ballpark figure, this can change depending on your specific decking, so don’t forget to double-check the manufacturer’s guidelines.

Height off the ground is another consideration. The more airflow you have underneath your deck, the cooler it’ll be, which can help to keep that expansion in check. And, don’t forget about drainage – no one wants a soggy deck, and it can also make the expansion and contraction worse.

And finally, watch those overhangs. While it might be tempting to extend them for a sleek finish, you’ll need to make sure they’re no more than 20mm to avoid any potential splitting.

So, while your composite decking will expand and contract a bit, don’t let that put you off. With the right planning, understanding, and a little bit of TLC during installation, you’ll have a fantastic deck that will keep looking at the business for years to come.

Check out some of the modern decking ideas in case you’re not sure what kind of deck is right for your yard. 

Safety Considerations

Safety is the paramount concern when it comes to any form of construction, and decking is no exception. Failure to account for expansion and contraction when installing a composite deck can yield adverse consequences.

These can range from minor annoyances such as loose and squeaky boards, to severe structural instability that can pose a risk to the safety of you and your family. Worst-case scenarios might see boards popping up or handrails becoming detached, leading to dangerous conditions.

In order to mitigate these risks, the correct fasteners should be employed. High-quality, durable screws and nails, specifically designed for use with composite decking, can significantly reduce the risks associated with expansion and contraction.

Also, following the recommended installation techniques as set out by composite decking manufacturers can further enhance the safety and durability of your deck. Make sure to consult one of the best decking installation services in London!


Safety Considerations

Maintenance and Longevity

It’s important to recognize that appropriate installation techniques extend beyond immediate safety concerns. They also contribute to the longevity of your composite deck.

By taking into account the potential for expansion and contraction, you’re ensuring that your deck can withstand the changes in temperature and humidity that come with the changing seasons, thereby improving its lifespan.

In terms of maintenance, composite decking requires far less attention than traditional wood decking. However, there are still steps that can be taken to minimize the impact of expansion and contraction.

Regular cleaning, particularly in the gaps between boards, can prevent the accumulation of water which can exacerbate these effects. It’s also advisable to clear the deck of any debris and to ensure that the drainage system is functioning correctly.

Final Thoughts

Understanding the role of expansion and contraction in composite decking is essential for anyone considering installing a deck, whether you’re a homeowner looking to improve your garden or a professional builder.

Taking these factors into account during the planning and installation stages can significantly improve the safety, appearance, and lifespan of the deck. By following the manufacturer’s guidelines, using appropriate fasteners, and maintaining the deck correctly, it’s possible to install a beautiful, durable composite deck that can be enjoyed for many years.

The key takeaway is this: proper planning and attention to detail during installation will yield a high-quality deck that not only looks great but also stands the test of time.