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Open timber cladding with reaction-to-fire class B

20/05/2025
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Good news for architects, specifiers and timber professionals: open timber cladding can now meet reaction-to-fire class B – a milestone in the world of outdoor timber applications.

Vertical cladding with open joints

For the first time, vertical timber cladding with open joints is possible in reaction-to-fire class B – a groundbreaking development the timber construction sector has long been looking forward to.

Since the change in the regulations on the reaction-to-fire class of timber cladding last summer, we have already had reaction-to-fire classification reports for our fire-retardant closed cladding with traditional fixing.

What is new is that there are now also certified solutions for open-joint cladding with a maximum gap of 8 mm. This aesthetic yet fire-retardant façade solution is now a reality thanks to a smart combination of fire-retardant treatment with polymers, considered design and careful installation. This means you can now apply open timber cladding vertically while meeting the strict requirements of reaction-to-fire class B.

This solution makes it easier than ever to opt for sustainable, natural and fire-safe building with wood – without compromising on design freedom.

Please note: for now, the certification does not yet apply to timber profiles with a colour finish. This is, however, being actively worked on.

Technical requirements for reaction-to-fire class B

  • Wood varieties: thermo ash, thermo clear pine, thermo pine
  • Boards with a minimum thickness of 19.5 mm and a width ≥ 72 mm
  • Vertical installation with a gap of ≤ 8 mm
  • Fire-retardant impregnated battens, 20 mm thick, fitted horizontally
  • Possible with or without a ventilation cavity
  • Substrate: all substrates of Euroclass A1 and A2-s1,d0 with a thickness ≥ 12 mm and a density ≥ 525 kg/m³
  • Traditional fixing on a timber support structure

Plus Line profile and made to measure

Within our range, two boards from the Plus Line profile are eligible for fire-retardant open-joint cladding. In addition, we offer made-to-measure solutions to align your project perfectly – both technically and aesthetically – with the requirements of reaction-to-fire class B.

INTERESTED IN FIRE-RETARDANT OPEN-JOINT CLADDING FOR YOUR PROJECT?