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Wooden cladding: how can it be effectively protected from fire?

Wood preservation
12.10.2023

Wood is one of the most fashionable building materials. Parquet flooring, panelling, decking and cladding have become essential elements in interior design and construction, thanks to their natural appearance and warmth. But how can you improve its reaction to fire performance ? What are the most effective methods?

Wood: a low-flammability material

Raw wood is by no means non-flammable , but contrary to popular belief, wood is not the most flammable material. Depending on its thickness, wooden cladding naturally falls between classes D-s2, d0 and D-s2, d2.

Softwoods, whether hard or with low moisture content, catch fire more than hardwoods over 14mm.

Burning wooden cladding to protect it from fire: the “Japanese” technique

Yakisugi (or Shou-Sugi-Ban) is a technique that involves charring the surface of the wood cladding to protect it from fire. The carbonisation of the visible surface of the cladding makes it rot-proof and resistant to fungi and wood-eating insects.

The wood of choice for yakisugi is cedar, which is very hard-wearing and has little fear of rotting. In Europe, it can be used on cypress, spruce and larch.

The disadvantage of this technique is that the wood will always look charred. It can be brushed, but this leaves little room for fantasy in terms of colour for the sawmills and manufacturers who use this process.

What’s more, working on each individual plank of cladding is more expensive for yakisugi than a more conventional fireproofing treatment .

Fireproofing products for wood cladding

To improve wood’s reaction to fire, there are two techniques for fireproofing wooden cladding : surface treatment or penetration treatment.

Fireproofing wooden cladding on the surface:

Surface fireproofing products can be found in the form of varnish or paint. They resist flammability in two ways:

  • or by forming a barrier and delaying the spread of fire (waterproof products),
  • or by burning until a protective layer is formed (intumescent products).

Thoroughly fireproofing wooden cladding:

There are also two techniques for thoroughly fireproofing exterior wood:

  • soakthe product: the product penetrates into it by a few millimetres
  • injecting the product into the wood : this is known as autoclave impregnation under vacuum and pressure for more in-depth protection.

Is there an environmentally-friendly alternative to flame retardants?

It will be possible to thoroughly fireproof wood using a more environmentally-friendly, PH-neutral, water-based, ready-to-use product.

Groupe Berkem has developed a new formula for a fireproof product designed for use in timber construction , including wooden cladding. The product is applied by vacuum and pressure autoclave impregnation and is suitable for both interior and exterior wood.

The product contains no volatile organic compounds (VOCs), which means better protection for the health of people who come into contact with treated construction timber, from the sawmill to the installer to the end customer.

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