A composite decking is a strong and durable building material that is used to make decks. Composite decking is made from recycled wood and plastics, so no trees are fallen to make the board.

The wood and plastics are then processed in factories and cut into various sizes so that they can be used for building decks. The board, when ready, will form one of the strongest deck materials that you can use to build a deck in your house.

Homeowners prefer composite decks because of the ease that comes with maintaining them. This is because there is no need for you to sand and oil composite decks to preserve them. 

Also, composite decks are more desirable than timber decks and will not wane when they are exposed to the ultraviolet rays of the sun. The installation process of composite decks is easy because you can choose between the surface installation and the hidden installation.

When installing composite decks, there are procedures that you must follow to make the process simple and to stick to best practice. One of those guidelines is to leave enough space between the composite deck board to accommodate expansion. The next section explains why composite decking expand. 

Why Plastic-Wood Decking Expand

Composite decking expand because of a change in the temperature of the location they are installed. High temperature makes the composite deck expand along its length and width.

Also, composite decking expansion depends on the materials that the decks are made of.

One thing about thermal expansion is that it can shift the composite decks from where they are fixed if enough space is not allowed between the decks.

This can lead to a situation where the decks will be weakened. So, you should make sure to check with your composite decks’ maker for advice so that you will know the expansion level of your deck. 

Things that Affects Composite Decking Expansion

There are some factors that affect composite decks expansion. They are heat, the deck’s color, and the location you place the deck. 


Remember that composite decks are made with wood and plastics. The plastics in the composite decks make them absorb heat when the decks are exposed to direct sunlight. 

So, when composite decks are exposed to high temperature, they expand at all sides. This usually occurs in hot regions, and the process is called the thermal expansion of composite decks.

Color of the Composite Decking

The color of your composite decking matters because it affects how your deck expands.

This is because dark-colored composite decks absorb heats more than light-colored composite decks. Dark brown composite decks, for example, will absorb heat than light brown composite decks. 

When this happens, the dark-colored composite decking will expand more than the light-colored composite decking. So, if you live in an environment that is hot, it is recommended that you choose composite decks that are light-colored.

Location of the Decking

Composite decks that are exposed to direct sunlight absorb heat more than decks that are positioned under shade.

This means that composite decks built in the garden or lawn will absorb heat more than composite decks that are built in the balcony.

Plastic-Wood Decking Gap

When you are installing your deck, you should not allow your composite decking board to meet at both ends.

You have to leave a space between the composite decks. This is to accommodate composite decking expansion gap.

The essence of leaving this space is for the decking to expand and contract when they heat up. 

The amount of space required depends on how often temperature changes where you live.

If you reside in hot regions that have frequent temperature change, you need to leave a larger gap than you would if you live in a region where the temperature doesn’t expand. 

Different makers of composite decks will provide various instructions on how to install your deck and the right amount of space that you should leave.

What is composite decking expansion gap

It is recommended that there should be a 5mm gap between the ends of your composite deck boards. 

So, when you are laying your composite decks on the joists, you must make sure that you leave at least 5mm space between the composite decks. 

This is so that when the composite decking expands, the decks will not warp.


Composite decking expand when they are heated or exposed to direct sunlight. So, it is advised that you leave a space of 5mm between the edges of the decks.