St Dunstans commercial composite decking with clear expansion gaps

Does composite decking expand and contract?

Composite decking contains a percentage of real timber. As such it will contract and expand in a similar way to wood decking, just on a smaller scale.

Why does composite decking expand and contract?

As mentioned above, a key reason for the expansion and contraction of composite decking is its construction. Composite decking is made from a combination of wood fibres, recycled plastics, and bonding agents. The wood content of the deck board will contract and expand, as it would if it was part of a fully timber deck board.

What causes composite decking expansion

There are a few things which can cause a composite deck board to expand. These include:

Heat – due to its composition a composite deck board will expand slightly when exposed to relatively high temperatures. This may be both in width and length.

Colour – dark colours can absorb more heat than lighter coloured boards. This means darker coloured boards may be more susceptible to expansion.

Location – as we’ve mentioned, heat can cause composite deck boards to expand. As such, it is important to consider the location of your new composite deck. If in full sun, there is the possibility that your deck boards will expand.

What causes composite decking contraction

The reasons a composite deck board may contract are identical to those that will make it expand. So all the above points are relevant when it comes to considering elements that will affect the contraction of your new composite decking boards.

Consider a composite decking expansion gap when constructing

To counteract the effects of expansion and contraction, you should use specialist spacers when installing your new decking. This will ensure that there is sufficient space between your boards for them to expand and contract without negatively impacting the fitting or integrity of your decking.

To find out more about expansion and contraction of composite decking, call our expert, friendly team today on 01978 667 840.


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