Much has been said about composite decking these days that make homeowners buy it. Makers of composite decking claim that their boards are easy to maintain, easy to clean, aesthetically pleasing, and resistant to the elements. Homeowners wanting to install a decking material will have no choice but to go for composite wood decking because of its advantages. But with wood plastic decking advantages comes its disadvantages. Mould is one problem of composite wood decking. If you plan to install wood plastic composite outdoors, you might wonder if composite decking will get mould. 

What Is Composite Decking?

A synthetic outdoor decking material. That is the short and simple definition of composite decking. Wood flour and recycled PVC are materials used to make a wood plastic composite. Unlike timber that must be treated with chemicals, composite wood doesn’t need chemicals. The boards are stronger and better than timber decking and will withstand the elements better than other decking types. 

What Is Mould?

Mould is a fungus which is a kind of plant that doesn’t have root, flower and leave. They come in various patterns, which can be black, white, green, or yellow. Mould can take any shape and form and need moisture to survive on a decking. They carry out a crucial role in breaking down organic matters like leaves, pollen, twig or trees. Mould will eat into a decking is left uncheck and can distort the beautiful appearance of the decking. Also, mould can cause structural damage to your decking. 

Is Composite Decking Resistant to Mould?

Makers of composite wood decking have long advertised their products as resistant to mould and mildew. This is one reason decking owners are purchasing composite decking boards. But is wood plastic decking mould resistant? The answer to that enquiry is yes. But it depends on the type of composite boards that you purchase. One thing to note about plastic wood decking is that it is not mould proof. This infers because if you leave your WPC decking uncheck, mould can attack it and destroy the beautiful surface texture. 

Composite Decking Is Mould Resistant

When you install your composite decking outdoors, you will discover that it was different from timber. One thing about composite boards is that they are resistant to the elements like rain, heat, and bad weather. Also, mould that attack wood will not attack composite decking. The reason for attacking timber is that wood is food for mould.

 Mould cannot feed on plastics. Remember that composite wood is a mixture of wood dust and plastic. The plastic covering of the composite boards will prevent mould from reaching its wood component. But recently, there has been a lawsuit against composite wood owners because most composite boards are destroyed by mould. But how is that possible since composite wood has a plastic covering.

Composite Decking Is Not Mould-Proof

Mould on a decking

One thing about composite wood is that it is not mould proof. This implies that if you leave your decking to uncheck, it can be attacked by mould. Mould feed on organic matter like leave or rotten pollen when they stay on the surface of your decking. If you let mould stick to the surface, your decking will lose its resistance and become susceptible to mould attack.

 Another reason mould will attack composite decking is that most decking boards are uncapped. Uncapped wood-plastic composite does not have the extra layers of protection that capped decking has. Most composite boards come in different capped options. There is the three-sided capped composite decking and the four-sided capped decking. If you install uncapped decking in your outdoor space, then you should expect mould to attack it. 

How to Prevent Mould Growth on Your Decking

One way to prevent mould growth on your decking is to install four-sided capped composite boards. Four-sided capped composite boards have a plastic coating on all sides. This extra layer of plastic prevents moisture and fungus from entering the boards. Since mould and mildew feed on timber, the plastic protection will stop their movement.

 Most decking makers produce three-sided capped boards. This is a compromising shortcut to reduce the cost of making the composite boards. 3-sides capped composite boards leave a side of the board exposed to mould attack. So, it is crucial to install 4-side capped boards that have all sides covered by plastic.


Composite decking will get mould if you don’t maintain it. Also, if you install uncapped composite boards, then mould will attack them. To ensure that your decking does not get mould, you should install 4-sides capped composite boards.

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