Mould is a problem for wood decking materials when it is installed outdoors. It will not only cause discolouration of the wood decking surface, but it will lead to decay. Composite decking was created to solve lumber decking problems. And since mould is one problem of composite decking, does composite decking get mould? That depends on the grade of plastic wood decking you purchase. Also, how often homeowners maintain their wood-plastic composite decking determines if it will get mould. This write-up considers mould as a decking problem and looks into conditions that might cause mould growth on composite decking. 

What Is Decking Mould?

A mould is a fungus. This fungus does not exist alone, but grows in the form of multicellular filaments called hyphae. Another way to see mould is as a multicellular, microscopic fungus that helps nature decompose dead organic materials found in the environment. Mould spores float in the air regularly until they find the right spots for them to germinate. That spot can be your home furniture, your decking or fencing. One mould land on your decking or furniture; it will feed on the organic materials in it, like lumber and leaves. 

One thing homeowners should note is that mould growth depends on the climate and weather.  A dry environment will not support mould growth. This is because the spores will have a hard time germinating. But a damp environment will support mould growth. The mould spores will quickly germinate and create a dark spot on your decking or fencing. Mould will continue the process of decaying until it has consumed the decking.

The problem with mould is not just with discolouring or creating dark spots on the decking or fencing. Mould will eventually lead to decay and might cause serious damage and safety issues with your decking. Remember that mould growth is responsible for decomposing organic matter in the environment. Once it reaches your decking and finds lumber or lumber products, mould won’t stop until it has finish decomposing. 

Will Composite Decking Get Mould?

Does Composite Decking Get Mould?

That depends on the grade of wood-plastic composite decking that you purchase. Recently, homeowners that purchase composite decking materials have brought several class actions against composite decking manufacturers. Those class action lawsuits are in response to the manufacturer’s claims that composite decking will not form dark spots. Note that mould causes dark spots on plastic wood decking. So, when wood-plastic composite decking becomes dark, it will discolour the surface texture and eventually destroy the decking. Homeowners that purchase composite decking want the assurance that their decking will not grow mould. 

But is composite decking resistant to mould? Plastic wood decking contains wood dust and plastics as its primary constituent. As a composite, plastic lumber decking is stronger and better than timber, hence the assurance that it will defeat most of the woes of wood. But mould is no ordinary woe. Mould attack anything organic on the surface that it comes in contact with it. If mould reaches the surface of your decking, it will attack the wooden part and destroy it. Remember that plastic wood decking is a mixture of timber and polymer. The timber part is exposed to the elements after you have installed the decking. 

When mould reaches the composite decking, the wood becomes a hot spot that supports mould growth when the weather is damp. Eventually, mould will enter the crevices of plastic wood decking and cling to the timber part and begins to decompose the decking. This will subsequently cause dark spots on the surface of your wood-plastic composite decking. Note that this will happen to the old-generation composite wood decking. The newer-generation plastic wood decking is quite different from the old one and has an extra protective shell on its surface. 

Composite Decking that Resist Mould

There are two kinds of wood-polymer decking. The first generation decking has little resistance to mould attack and the newer-generation decking. The difference between the newer generation and the old composite decking is that the former has a protective shell covering the surface, while the latter does not. The protective shell of the newer generation composite decking is made of plastic. The plastic covers the plastic wood decking board and prevent moisture and mould from reaching the wood. Since mould destroys wood, newer generation composite will not get mould if you maintain it. 


Does composite decking get mould? That depends on whether you install the newer generation decking or the old one. You should install a composite decking that has a protective shell on its surface that conceals the wooden part. 

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