What Is Wood Plastic Composite WPC Decking Made Of?

If you’re planning on building a deck and have been researching the different types of decking materials available then you’ll definitely have heard of wood plastic composite decking.

It’s a versatile material that has many useful properties and it’s renowned for its durability and longevity.

But, what is it actually made of?

In this article, we’ll answer that question and take a look at the manufacturing processes that are used to make it as well. We’ll also examine some of the reasons behind composite decking becoming so popular.


Wood Plastic Composite Materials

Wood plastic composites are made from a mixture of recycled plastic and reclaimed wood particles.

Although wood plastic composite decking is sometimes confused for plastic decking it actually has a higher content of wood than plastic, and its plastic content is usually high-density polyethene.

The material makeup of most composite decking is usually around 70% wood particles and 30% recycled plastic. This gives wood plastic composite several advantages over other materials such as wood decking and plastic decking as it combines the best properties of both.


The Early Days Of Wood Plastic Composites

When wood plastic composites were first being manufactured it was common for oyster shells, rice hulls and walnut shells to be used as fillers when making the material. This was cheaper for manufacturers and allowed them to maintain a steady level of quality.

However, as they tried to cut back on costs even further they started to add more and more of these fillers to the wood composite mix. This gradually led to the strength and integrity of the product being compromised and losing its flexibility.

To combat this, manufacturers started using organic material from sawmills such as wood sawdust to create their WPC products. This proved to be an affordable way to produce the products without compromising their quality.

It was also a much more eco-friendly way to produce their products and meant that their composite decking boards could imitate the look of natural lumber.

Due to the success of this mixture of wood flour and recycled plastics, the same combination is still used today.


The Wood Plastic Composite Manufacturing Process

Wood plastic composite is generally formed using a two-step manufacturing process.

Firstly, the wood flour is mixed with recycled plastic which is usually high-density polyethene. This mixture is then melted down into a dough-like consistency. The mixing of the two materials is either carried out by batch or by a continuous process.

Depending on the manufacturer, other ingredients will also be added to the wood composite mix. These can include a stabilizer, plastic coupling agent, foaming agent, and one or more dyes. Lubricants are also often used to enhance the appearance of wood-plastic composites.

Once the material has been mixed and melted there are three different methods that utilise different mechanical properties to shape it into composite decking boards or other products.



The most common method is called co-extrusion in which the molten wood plastic composite is forced through a die. This is a metal channel that forms the material into a specific, desired shape.

There are a number of different extruder types with varying mechanical properties such as a double screw or single screw. These extruders are used to achieve different shapes for the final products.


Injection moulding

Injection moulding is a different process from co-extrusion that is also used to form wood plastic composites into their final shape.

During this manufacturing process, the molten material is injected into a mould cavity at high pressure. Once the mould is filled the material then solidifies and settles into the desired shape.


Compression moulding

The third process used to form wood plastic composites into their desired shape is compression moulding. During this process, the material is forced in between two mould halves and then the mechanical properties of the mould are utilised by exerting pressure on both sides.


Why Are Wood Plastic Composites So Popular?

So, now you’re up to speed on what wood plastic composites are made of and how composite decking is formed. You may now be wondering why it’s such a popular material when compared to solid wood or 100% plastic products.

There are many reasons why composite decking is quickly overtaking both wood decking and plastic decking as the go-to choice for both homeowners and industry insiders.

Let’s take a look at some of the reasons that composite decking has become so popular.



Unlike solid wood decking, composite decking is very resistant to rot due to the plastic content of the deck boards. This makes it resistant to water which means rot can’t take hold which gives composite boards amazing durability.

This also means that composite decking boards are very long-lasting as they don’t begin to rot over time as real wood does. On average, composite decking last for between 25 and 30 years.



Another reason that composite decking is so popular is that it requires far less maintenance than other decking materials such as wood. It doesn’t need to be treated, sealed, painted, or stained to maintain its durability and longevity.

Composite boards only require basic cleaning which can be done with a traditional pressure washer or warm, soapy water and a soft bristle brush. The fact that they require such little care leads to greatly reduced maintenance costs which will save you money over time.


Environmentally friendly

Wood plastic composite is also the most eco-friendly choice for decking materials. As it’s made with recycled plastics and reclaimed wood it means that no trees are felled to make it and the amount of plastic that goes to landfills is reduced.

Unlike plastic decking, no harmful chemicals are released into the atmosphere during production which means composite has a low environmental impact.

The fact that no sealants or stainers need to be used to maintain it also reduces its environmental impact.


UV resistance

Composite boards are very resistant to UV light and don’t fade much over the course of their service life. A small amount of fading does occur within the first few months after installation, but this process slows down and eventually ceases so that the boards retain their colour. There is more fading with the Clarity decking range.


Slip resistance

Due to the materials that it’s made of, a WPC deck is very slip-resistant and ideal for wet climates and installation near swimming pools. Its water-resistant properties mean that water tends to evaporate from its surface very quickly.

Typically, you can expect a composite deck to be dry within 30 minutes of water exposure. The wood grain finish and grooved surfaces of composite boards provide good traction underfoot. This leads to a reduction in slip hazards and makes them a safer choice than wood.



As composite boards are made with both plastic and wood they have the appealing finish of traditional timber with the practicality of synthetic materials. This gives them a contemporary appearance that can complement any home and garden.

Our Ecoscape composite boards also come in a wide range of attractive colours such as charcoal, walnut, spiced oak, argent, ash, autumn, and silver birch. They’re as easy to cut and install as wood boards meaning they can fit nicely into outside spaces of all shapes and sizes.


Warp resistance

Although composite boards do expand and contract as temperatures fluctuate, they are designed to withstand these changes in size and don’t warp in the same way that wooden boards would.

Solid wood boards are very prone to water absorption which causes them to expand and contract much more significantly than composite boards. This leads to them cracking, warping and splitting over time.

However, composite boards will still absorb heat when exposed to the sun for long periods of time and will feel hot to the touch. This is perfectly normal and won’t result in any damage to the boards. If you want to reduce heat absorption then you should opt for light colours instead of dark ones.



Is composite decking more expensive than timber decking?

Composite boards are more expensive than wooden boards in terms of their upfront costs. On average, it costs around £40 per square metre for uncapped composite boards and around £80 per square metre for capped composite boards.

Wooden boards vary widely in price depending on the type of wood but almost all of them will be cheaper than composite. However, as composite boards don’t need to be treated or sealed you will save money in the long term.


Can I paint composite boards?

Although composite boards don’t need to be painted it is still possible to do so. If you intend to paint them, you should use a polymer primer and then a layer of acrylic paint. However, this will lead to increased maintenance requirements as you will then have to repaint the boards fairly regularly.


Is wood plastic composite insect-resistant?

As WPC contains plastic it is inedible to insects. This means that, unlike traditional timber, you don’t need to worry about insects burrowing into the core of composite boards. Insects are naturally repelled by the mixture of wood and plastic.


Are wood plastic composites toxic?

Unlike UPVC decking, composite decking is made without the use of toxic chemicals. When UPVC is made harmful chemicals are released into the environment which contributes to the pollution of the air, land, and water. This is not the case for wood-plastic composites.


Final Thoughts

Wood plastic composite is a fairly unique material that combines the best elements of both real wood and synthetic plastics. It can be constructed using three different processes that all achieve similar ends and lead to the same excellent results.

As you can see, the amazing properties of this material give it many advantages over other types of decking and its popularity looks set to keep on increasing.

If you’re looking for a durable and versatile material to use for your decking project then you need to look no further than our Ecoscape wood plastic composite.

Gary is the founder and CEO of Ecoscape UK. Gary graduated from Liverpool JM University in 2007 with a 2:1 in Economics. A passion for innovation, design and sustainability, Gary has put to market numerous wpc products/systems, some of which have UK and European registered designs. Outside of work Gary enjoys spending time with his family, the great outdoors and watching Manchester United.