What Is Wood Plastic Composite (WPC) Decking Made Of?

Wood plastic composite (WPC) decking is made from a combination of wood fibres, plastic polymers and small amounts of additives. The wood provides structure and a natural appearance, while the plastic helps protect the material from moisture and everyday wear.

The exact ingredients and proportions vary between manufacturers, but most WPC decking uses wood flour or fibres blended with polyethylene or another suitable plastic.

Let’s look at what goes into composite decking boards and what each material contributes.

What materials are used in WPC decking?

WPC decking typically contains three main components.

Wood fibres or wood flour

The wood component usually comes from finely processed wood particles, sawdust or reclaimed wood fibres.

These provide part of the board’s structure and contribute to its wood-like appearance.

Wood content varies between manufacturers, so not every composite decking board contains the same proportion of timber material.

Plastic polymers

The plastic component binds the wood fibres together and helps improve moisture resistance and durability.

Common polymers include:

• High-density polyethylene (HDPE): Frequently used in composite decking, including products containing recycled plastic.
• Polypropylene (PP): Another polymer used in some wood plastic composites.
• Polyvinyl chloride (PVC): Used in certain composite formulations, although all-plastic PVC decking is a different product category.

The type and quality of polymer influence the characteristics of the finished board.

Additives and colour pigments

Manufacturers may include additional ingredients to improve processing, appearance and performance.

These can include:

• Colour pigments: Create different board colours and finishes.
• UV stabilisers: Help limit the effects of sunlight.
• Coupling agents: Improve bonding between wood fibres and plastic.
• Processing additives: Help achieve a consistent material during production.

The precise formulation depends on the manufacturer and decking range.

What percentage of WPC decking is wood and plastic?

There isn’t one standard wood-to-plastic ratio for all composite decking.

Some boards contain a higher proportion of wood fibres, while others use more polymer or additional materials.

Ecoscape has published a formulation containing approximately 55% reclaimed wood fibres and 45% recycled HDPE for its composite decking. However, material specifications can vary between product ranges.

When comparing WPC products, it’s worth checking the manufacturer’s technical information rather than assuming every board has the same composition.

Is WPC decking made from recycled materials?

Many WPC decking products incorporate recycled plastic and reclaimed wood fibres.

Using reclaimed materials can reduce demand for virgin raw materials, although recycled content varies between manufacturers and products.

Ecoscape uses recycled materials in its composite decking ranges, alongside wood fibres sourced through its stated responsible sourcing arrangements.

However, recycled content alone doesn’t determine a product’s overall environmental impact.

For a fuller discussion, see Is Composite Decking an Environmentally Friendly Option?.

What’s the difference between WPC decking and plastic decking?

Although the terms are sometimes confused, WPC decking and plastic decking aren’t identical.

WPC decking combines wood fibres with plastic polymers.

Plastic decking, such as all-PVC decking, is manufactured primarily from plastic without the same wood-fibre component.

This difference affects the composition, appearance and material characteristics of the boards.

WPC also comes in different constructions, including capped and uncapped boards. Capped composite decking has an additional protective polymer layer surrounding some or all of the core.

For example, Ecoscape’s Clarity composite decking is an uncapped WPC product.

How are these materials turned into decking boards?

The wood fibres, polymers and additives are combined and processed to create the finished composite material.

Manufacturers then shape the mixture into decking boards, commonly using extrusion.

Some products receive an additional protective outer layer during manufacture.

For a detailed explanation of these production methods, read How Is Composite Decking Made?.

Final thoughts

Wood plastic composite decking combines wood fibres, plastic polymers and performance-enhancing additives to create an alternative to traditional timber or all-plastic decking.

While the basic ingredients are similar across many WPC products, the proportions, polymer types and additional materials vary.

Understanding these differences helps explain why composite decking boards can have different finishes, characteristics and performance specifications.