Discovery in CLT passive fire protection

Using cross-laminated timber in construction has become much easier following some new industry research. This refers to a study commissioned by Willmott Dixon. It eliminated a technical gap that had been creating uncertainty and delays in the use of cross-laminated timber (CLT) projects in the construction sector. But what are the features of this project, and how might it influence the construction industry in the future?

The main source: CLT passive fire protection breakthrough

What are the features of the discovery?

Previously, all CLT projects required individual technical assessments. Now, certified solutions exist for projects using cross-laminated timber (CLT) and Siderise cavity barriers in both walls and floor assemblies.
The testing programme was carried out at the Siderise Innovation Centre in Maesteg with support from Willmott Dixon and CLT manufacturer KLH.
The tests examined three critical interface scenarios commonly found in CLT building projects:

CLT walls in a vertical configuration, joining a cavity barrier (tested in accordance with EN1366-4)
CLT floor-to-wall interfaces in a horizontal configuration with a cavity barrier (tested in accordance with EN1366-4)
CLT connections with floor and wall in a horizontal configuration with a cavity barrier for use in rainscreen systems (tested in accordance with TGD19 prEN1364-6)

All three tests were completed, covering worst-case scenarios, including 100-millimetre five-layer CLT panels tested to strict European standards.

How may CLT passive fire protection influence the UK building industry?

The tests confirmed the effectiveness of cavity barriers across multiple CLT configurations, demonstrating their ability to prevent fire spread through concealed spaces—an essential safety requirement in timber construction. The worst-case scenarios tested included 100-millimeter five-layer CLT panels, providing design teams with confidence in the solution’s performance under typical project specifications.
Fencyx, as one of the leaders in the UK building industry, positively reacts to this trial. We are confident that this research will open new pathways for the use of CLT, supporting the further development of the construction sector.