Reaction to fire regulations for cladding have changed

New rules covering the reaction to fire classes for timber cladding came into effect on August 20, 2024. Although the change seems minor, just adding the word “untreated” to the CWFT table, it has major implications for using wood cladding on buildings. Here we explain what has changed and how it will impact your choices.

Wat is the CWFT table?

CWFT (Certified Without Further Testing) is a European provision which groups wood products into reaction to fire class D, without further testing being necessary, where certain conditions are met. Until recently, it stipulated that wood cladding met Class D reaction to fire standards where this referred to closed joint façade systems with a minimum thickness of 18 mm and a density of at least 390 kg/m³.

Over time, it became clear that the term “wood” in the regulations was being interpreted too broadly, leading to erroneous assumptions about fire safety. In fact, the CWFT standards were never designed for treated or modified cladding. But this type of wood was often incorrectly included in them. To avoid any confusion and reduce the risk of fire, Europe has amended the standard by replacing the word “wood” with “untreated wood”. This means the CWFT table no longer covers any types of treated wood, so specific fire resistance certificates are now required to meet the standards.

Implications for the construction industry

The amended rules mean architects, entrepreneurs and property developers need to be very aware of what type of wood they are using. The CWFT table used to be a straightforward solution, but now additional fire tests and fire resistance certificates guaranteeing the safety of treated or modified wood varieties are generally required. This means that a fire certificate will always be necessary now when using treated timber for cladding.

Carpentier's solutions

Carpentier is constantly investing in expanding its range of timber cladding that comes with a reaction to fire certificate. We currently offer two options for using our cladding in full compliance with current regulations, without compromising on fire safety or style.

• Option 1: Closed joint cladding in thermally-modified wood reaching Class D or Class B reaction to fire levels without fire-retardant treatment

  Our range includes a broad selection of thermally-modified varieties of wood that are Class D certified, and also Class B, without fire-retardant treatment. These closed joint profiles meet the new regulations and come with the required fire resistance certificates. These are available online and can be easily downloaded using your personal login.

  Using HOTwood bamboo in the Switi project

  A good example of our HOTwood bamboo Shiplap QC used as timber cladding is the Switi project in Amsterdam. This closed joint cladding profile meets the B-s1, d0 reaction to fire standard without fire-retardant treatment.

  For this project for biosourced new housing, we supplied no less than 4,000 m² of this high quality, fire-retardant timber cladding. The project won a National Timber Construction Award 2024 in the Netherlands in the serial timber constructioncategory because of its sustainable and innovative approach.

  

• Option 2: fire-retardant treatment for your chosen cladding

  For projects requiring heightened fire safety measures, we can offer additional fire-retardant treatment to improve the reaction to fire classification. The wood will be treated in vacuum conditions in an autoclave, using a fire-retardant product based on 100% natural ingredients.

  
  Here are the Class B fire-retardant cladding profiles

Good news for open joint cladding

In 2025, together with the company Grad, we are launching a new fire-retardant clip. Thanks to this innovation, and on condition a fire-retardant treatment is applied, we will be able to achieve Class B standards, even for ceiling and façade cladding systems with open joints of up to 30 mm. This solution means we can combine the stylish advantages of open joint systems with the required fire safety levels.