Is composite decking flammable? Check how safe WPC is!

What exactly is a composite decking board?

Before we get into the specifics of fire, it’s worth reminding ourselves what composite decking boards are actually made of.

A composite decking board is made up of:

• wood flour (approx. 30–60%),

• plastic (most often PE, HDPE or PVC),

• additives (e.g. pigments, UV stabilisers, antifungal agents).

Sounds like a mixture of wood and plastic? That’s exactly what it is. This material combines the benefits of both components: the appearance of wood and the durability of plastic.

All right, but is a composite decking board flammable?

It depends. No material is 100% non-flammable (well, perhaps apart from concrete), but composite decking boards have varying levels of fire resistance, depending on their composition and manufacturer.

Composite decking boards can fall into different flammability classes, including:

• Bfl-s1 – low flammability, very limited smoke production (the best class for flooring),

• Cfl-s1 – moderate flammability, little smoke,

• Dfl-s1 or Dfl-s2 – higher flammability.

👉 The further along the alphabet the letter, the greater the risk of the board catching fire.

What do European standards say?

In Europe, the flammability of composite decking boards (and other building materials) is governed by the EN 13501-1 standard, which assigns fire resistance classes.

For flooring (that is, terraces and balconies), the most common classes are:

• Bfl-s1 – difficult to ignite, limited smoke production,

• Cfl-s1 – moderately easy to ignite, but without excessive smoke.

Boards in class E or F meet practically no safety standards and should be avoided in areas intended for use.

Composite decking boards versus wood – who wins the fire test?

This may come as a surprise! Although many people consider wood to be “naturally safe”, untreated wood can be more flammable than some composites.

Comparison: 

As you can see, a well-made composite decking board can be safer than wood – especially if it meets high fire safety standards.

How can you improve fire safety when installing composite decking boards?

Choosing the material is one thing, but correct installation is also extremely important. Here are a few practical tips:

• Choose boards with a Bfl-s1 or Cfl-s1 certificate
• Avoid laying decking boards directly over an open flame (e.g. near a barbecue or fireplace)
• Maintain suitable gaps between decking boards to allow heat to dissipate
• Invest in non-combustible substructures (e.g. aluminium ones)
• Clean the terrace regularly – leaves and dust can catch fire quickly

What about in the event of a fire?

Composite decking boards, especially lower-quality ones, may start to melt and release toxic fumes, just like other plastics. That is why it is always worth choosing products with certification and a fire classification certificate.