Research commissioned by Willmott Dixon has eliminated a technical gap that has created uncertainty and delays in the use cross-laminated timber (CLT) projects in the construction industry.
Previously, all CLT projects required individual technical assessments. Now, there are certified solutions for projects using cross-laminated timber (CLT) and Siderise cavity barriers in both wall and floor applications.
The testing programme was conducted at Siderise's Innovation Centre in Maesteg with support from Willmott Dixon and CLT manufacturer KLH.
The tests examined three critical interface scenarios that appear across CLT construction projects:
- CLT wall interfaces in vertical configuration with EW-CB 30 Cavity Barrier (tested to EN1366-4)
- CLT floor and wall interfaces in horizontal configuration with EW-CB 30 Cavity Barrier (tested to EN1366-4)
- CLT floor and wall interfaces in horizontal configuration with RH25 90/30 Cavity Barrier for rainscreen applications (tested to TGD19 prEN1364-6)
All three tests were passed, covering worst-case scenarios including 100mm five-layer CLT panels tested to rigorous European standards.
The absence of standardised testing for cavity barriers on CLT has meant that every project has required bespoke technical assessments, creating inefficiency in design processes and uncertainty around fire safety performance. The new test data provides design teams across the sector with certified solutions that can be specified with confidence, Willmott Dixon says.
"This testing addresses a genuine technical gap that affects every organisation working with CLT," said Willmott Dixon architectural technologist Jessica Winyard. "By working collaboratively with Siderise and KLH to develop these solutions, we're helping to accelerate the adoption of low-carbon construction methods while ensuring robust fire safety performance."
The testing validated Siderise's EW-CB and RH25 cavity barriers across multiple CLT configurations, demonstrating their effectiveness in preventing fire spread through concealed spaces, a critical safety requirement in timber construction. The worst-case scenarios tested included 100mm five-layer CLT panels, providing design teams with confidence in the solution鈥檚 performance across typical project specifications.
According to Willmott Dixon, the implications for architects, engineers and contractors working on CLT projects are 鈥渋mmediate and practical鈥�.
- Standard cavity barrier details can now be specified without project-specific fire testing
- Design programmes are streamlined, removing delays associated with bespoke assessments
- Fire safety performance is backed by certified test evidence to EN1366-4 and prEN1364-6 standards
- Risk is reduced through proven solutions for vertical walls, horizontal floors and rainscreen applications
Siderise director of testing & project engineering Chris Mort added: 鈥淥ne of the primary goals of investing in the Siderise Innovation Centre was to provide the industry with the means to back their designs with robust test data, helping them achieve compliance and deliver safer buildings without compromising on design. We were delighted to support Willmott Dixon with the development of standard details for the CLT projects, and our learning from this process has been invaluable for expanding our own understanding of the demands of such an innovative structural system.鈥�
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