UK’s Willmott Dixon Completes Industry-First Fire-Safety Tests for CLT Construction

Willmott Dixon has completed an industry-first fire-safety testing program focused on cavity barriers used in cross-laminated timber (CLT) construction, Business Enquirer reported (11-10-25). The initiative fills a long-standing gap in understanding how cavity barriers perform across wall and floor interfaces in timber-panel buildings.

The tests, conducted with Siderise and CLT manufacturer KLH UK, covered three interface scenarios:

1. CLT walls in vertical configurations using EW-CB 30 cavity barriers.
2. CLT floor-to-wall horizontal configurations using EW-CB 30.
3. CLT floor-to-wall horizontal configurations in rainscreen applications using RH25 90/30 barriers.

All were tested under “worst-case” conditions with 100 mm five-layer CLT panels and achieved certified performance.

According to the companies, standardized, certified test data will now enable CLT projects to specify cavity-barrier solutions without bespoke assessments—reducing design delays, cost, and uncertainty while supporting wider adoption of timber construction.

Broader uptake will depend on regulators and building-control authorities recognizing the new standards, Business Enquirer reported. The results position CLT to compete more effectively with conventional construction methods while advancing the UK’s low-carbon building goals.