Composite Deck

How much space do you leave between composite decking boards?

In the process of building a new composite deck, one of the things that you need to take into account is the amount of space that has to be left between the boards. If the gaps between the composite decking boards are either too large or too small, potential problems may occur later on.

So how much space do you need to leave between composite decking boards?

Most of the time, the gap we leave between the composite decking boards will be anywhere between 5 -12mm. Because it does not expand as much as a timber deck does, composite decking boards may have gaps that are smaller than those of timber decks. Any gap that is more than 20mm might potentially cause safety concerns.

Why is it Necessary to Leave Gaps Between Your Composite Decking Boards?

There are two primary reasons why you should still leave gaps between the decking boards.

  1.  The expansion of the deck material 
  2.  The drainage and drying of the deck 

Deck Material Expansion and Expansion

Composite decking material will still expand when exposed to heat and cold for a long period of time, despite the fact that it does not expand as much or as often as timber decking does. When you leave space between the composite decking boards, you are providing the decking boards with the space it may need to expand without causing any damage to the boards. When the decking boards are placed closely to one another, they are more likely to sustain damage over time or to warp.


Given that your deck is located outdoors, it is exposed to a wide range of climatic conditions such as the heavy rains in Melbourne. Having a gap between the decking boards and the ground enables the water to drain and helps to keep your composite deck dry. It helps to prolong the life of the decking structure by preventing water from accumulating on your deck.

In addition, the spaces make it possible for the deck to dry more quickly below, and they also make it possible for the soil and ground area underneath your deck to “breathe” and keep dry. When soil under the deck is left wet constantly, it can develop mildew, which may result in “soft soil,” which can cause damage to your deck and perhaps even the foundation of your home. 

Since more than a decade ago, Superdeck has established itself as a reputable bespoke composite deck supplier and builder in Melbourne. In the event that you are interested in building a stunning composite deck for your home, you can contact Superdeck to get design ideas and installation quotes.

A deck builder from Superdeck will visit your residence with composite deck samples, collect measurements and have a discussion with you about the ideas you may have for your deck space. When that is complete, we will provide you with an estimate of when your project will begin and also a free quote for you.