CLT fire protection

4 26 2023 | Fire protection | Fire regulations | wood construction

CLT fire protection according to fire class B-s1, d0 requirements

Wooden CLT elements are commonly used in construction thanks to their good properties. Now it is possible to reach certified reaction to fire performance for CLT as per fire class B-s1, d0 in a sustainable way. 

CLT is a cross-laminated wood product with excellent values regarding visual and structural planning, cost efficiency and environmental aspects. Also, the fire resistance of CLT boards, elements and block elements as such is good. 

However, a reliable fire protection solution for the visible surfaces of CLT is often required. In many applications like interior walls and ceilings, there is a need to meet specific fire performance requirements. Nordtreat provides an excellent certified solution for this need.




Cross-laminated timber manufactured according to EN 16351 has been classified to meet reaction to fire class B-s1, d0 according to EN 13501 when treated with NT DECO flame retardant. This applies to interior CLT structures and features certified reaction to fire performance.

This means that when interior surfaces of CLT elements are treated with NT DECO flame retardant according to Nordtreat guidelines and the treatment is duly documented, the fire protection meets fire class B-s1, d0 requirements.

Read more about CLT fire protection solutions




Treatment with bio-based NT DECO flame retardant increases the fire safety of CLT buildings without compromising the environmental values of CLT. NT DECO is the first flame retardant in the world with a verified EPD (Environmental Product Declaration). 


NT DECO is a durable and cost-efficient flame retardant solution for the following reasons:


  • Certified reaction to fire performance along fire class B-s1, d0 (EN 13501-1)
  • Durable fire protection: in interior use, maintenance treatment is needed only if the surface is scratched
  • Preserving wood’s natural look and feel with a clear or translucent toned finish
  • Very low VOC emissions 
  • Enables wood’s natural breathability 
  • Practical and economical one-product solution: no need for additional primers or coatings
  • Safe and suitable for industrial and on-site treatment
  • Features the following classifications and certificates: 
    • A+/M1 emission classes
    • LEED v4 
    • KIWA
Published EPD and comparisons of the Co2 print of NT DECO treated CLT and gypsum sheeted CLT are available at request. 


CLT is manufactured according to the European standard EN 16351. Some manufacturers still hold European Technical Assessments (ETA) as approval for the use of CLT in building and construction. Both ways create a suitable basis for CE marking of CLT.

CLT interior surfaces can be fire-protected off-site under the manufacturer’s control and responsibility before assembling. Another option is to conduct treatment in a treatment facility or as on-site treatment once erected. In these cases, the treatment company is responsible for using the right treatment methods and documenting the process.

  • Nordtreat provides clear treatment guidelines for industrial CLT manufacturers
  • For treatment companies, Nortreat provides a detailed training program and partnership

An industrial manufacturing partner of Nordtreat or a treatment company authorised by Nordtreat is a reliable way to meet B-s1, d0 requirements. 

To learn more about the network of authorised flame retardant treaters, contact Nordtreat.  


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