The transition officially began in March 2025, when BS 476 started being removed from Approved Document B. From 2029, only systems tested to the EN 13501-1 standard will be accepted. Unlike BS 476, which focused on small-scale testing of individual materials, EN 13501-1 requires full system testing. This includes large-scale methods like BS 8414, which looks at how fire spreads across a complete façade, as well as BS EN 1364-1 and BS EN 1365-1, which assess fire resistance and compartmentation inside buildings.
The shift reflects a wider move towards assessing how materials perform together, rather than in isolation. That means insulation, cladding, fixings, and fire barriers must be tested as one system, not just approved on their own. While Euroclass ratings such as A1 or A2-s1,d0 still apply, having compliant materials alone is no longer enough. Under EN 13501-1, there must be evidence showing how the full wall build-up performs when installed.
Joe Ragdale, Technical Director at Wetherby Wall Systems, explains: “It’s no longer just about ticking the box on individual materials. You need to know how the whole system behaves in real conditions.”
This approach helps address risks that aren’t always obvious during design. Even if every component meets the required classification, combining them in a certain way can lead to fire spread, smoke production or structural failure. Testing the full system helps reduce that risk.
Despite the shift already being underway, many buildings remain behind. As of February 2025, only 46% of high-rise buildings applying to the Building Safety Fund for non-ACM cladding work had completed the remediation process. Meanwhile, costs linked to cladding remediation have passed £16 billion, with developers and contractors increasingly expected to share responsibility.
The Building Safety Act 2022 also introduces stricter duties for Principal Designers, Contractors and Accountable Persons. It includes a 30-year retrospective liability period for some claims and requires safety information to be recorded throughout the life of a building. For many projects, that means short-term decisions made today could carry long-term consequences.
To avoid disruption later, developers and design teams should be checking that wall systems are tested to EN 13501-1 and that supporting documentation covers the entire assembly. As the regulations continue to tighten, early action remains the simplest way to stay compliant and avoid risk.