In September 2024, the UK Government confirmed the withdrawal of the National Classes fire testing standards from Approved Document B, signalling a formal shift towards the EN 13501 series of European classification standards.
The publication of BS 476 in 1932 established a framework for evaluating the fire performance of construction materials and components. Over time, it expanded into a suite of parts addressing different aspects of fire performance covering reaction to fire (i.e. the behaviour of construction products in the early stages of fire, focussing on fire spread and growth) and resistance to fire (i.e. the behaviour of construction products in the later stages of fire, focussing on structure and containment).
For example, BS 476 Part 22, used alongside Part 20, assesses the fire resistance of non-load-bearing elements such as partitions and doorsets. Each test produces a detailed report, including the conditions under which testing was conducted, and the performance achieved. These reports have long served as supporting evidence for the performance of construction products in fire test conditions and continue to be used to demonstrate compliance with the fire safety requirements of building regulations in the UK and in other parts of the world such as Hong Kong and the United Arab Emirates.
The scope of application of products tested to the relevant part of the BS 476 suite of standards can be assessed using expert judgement, following guidance from the Passive Fire Protection Forum (PFPF) and using sufficient and relevant test evidence. Assessments are prepared by competent professionals with a deep level of knowledge of the product and its behaviour in fire test conditions and provide an opinion on the performance of the assessed designs if they were to be tested to the requirements of the appropriate test standard. However, the methodology behind such extensions differs markedly from that used within the EN classification framework – a distinction that adds complexity to the current transition.
THE EN 13501 CLASSIFICATION FRAMEWORK
Developed by the European Committee for Standardization (CEN), EN 13501 provides a harmonised system for testing and classifying construction products. It supports the Construction Products Regulation (CPR) by offering a consistent technical language across Europe.
"The EN 13501 framework is used in UK building regulations to provide the performance requirements for regulated and non-regulated construction products.
Under EN 13501, performance is determined through a series of standardised test methods, supported by provisions for Direct Application (DIAP) and Extended Application (EXAP). These define how test results may be applied to variations of the tested product, such as changes to the dimensions, finishes and components, while maintaining the performance classification established by the test evidence. Oversight of these rules rests with CEN working groups comprising international fire-testing experts, ensuring continued technical consistency.
Although initially designed to facilitate trade within the EU, the EN 13501 framework is used within UK building regulations to provide the performance requirements for regulated and non-regulated construction products. The performance requirements are linked to the type of product and the design and use of the building.
THE RATIONALE BEHIND THE SHIFT
Historically, both BS 476 and EN 13501 were recognised within Approved Document B as valid means of demonstrating compliance. However, the UK Government has committed to a single, unified system, aligning with the recommendations of the Hackitt Report for greater transparency and consistency in building safety regulation.
The withdrawal of BS 476 is being implemented in stages. A six-month transition for reaction-to-fire and external roof exposure tests concluded in March 2025, while a five-year period ending September 2029 applies to resistance-to-fire classifications. Specific exemptions remain for projects already underway. The phased approach aims to allow the industry to adjust to EN 13501 while minimising disruption to product supply chains and project timelines.
TECHNICAL AND OPERATIONAL IMPLICATIONS
For specifiers, contractors and consultants, the transition to EN 13501 introduces several important considerations:
• BS 476 results cannot be used to obtain EN classifications. New data must come from EN-specific test methods.
• EN rules for DIAP and EXAP differ from those used in BS 476. This will mean that a test programme previously conducted based on the BS 476 series of standards will not generate the same scope if it were to be repeated for the purpose of EN classification.
• Extensive re-testing may be required, particularly for manufacturers with wide product ranges.
• Some systems may need modification to provide the required level of performance to the EN test methods.
For consultants and contractors, the change also affects how performance evidence is communicated within specifications. EN classification reports communicate the performance characteristics of a product using a classification system with each letter and symbol relating to a specific property of fire performance as defined in the relevant part of EN 13501 (e.g. E for integrity and R for load bearing) whereas the fire resistance performance under the national system, using BS 476 evidence, is typically communicated in terms of the results generated according to the standard.
For construction products with reaction to fire performance, both the EN classification and national system communicate performance using classes. However, the two regimes are distinct from one another and no equivalence in performance can be drawn between the two. It is therefore important to understand the EN 13501 classification system to ensure construction products are correctly specified for their end use within the building.
PREPARING FOR THE TRANSITION
The most effective way to manage the shift is through early engagement with accredited test laboratories. Manufacturers are encouraged to catalogue their product ranges and share these details with testing partners to plan suitable EN programmes. Because EN testing requires precise knowledge of DIAP and EXAP rules, working with laboratories experienced in these methods is vital. Warringtonfire, for instance, has more than 20 experts involved in CEN working groups that help develop EN test, EXAP and classification standards for products including doorsets, fire stopping, roofs and wall systems. This technical expertise supports accurate classification and smooth adaptation to the European framework.
SUPPORTING INDUSTRY THROUGH CHANGE
Following the government’s consultation, industry concern has centred on the capacity of UK laboratories to accommodate the surge in EN testing demand. Warringtonfire’s network of UKAS-accredited laboratories in the UK, together with a BELAC-accredited site in Belgium, provides capacity across reaction-to-fire and resistance-to-fire testing for a wide range of product types.
Warringtonfire’s sister company BM TRADA has also introduced three new Q-Mark Certification schemes for timber, metal, and composite doorsets, and updated an existing one to align with the upcoming regulatory changes in England. The Q-Mark schemes offer a clear pathway to third-party certification, ensuring products meet high safety and performance standards. They include ongoing assessments like Factory Production Control audits and periodic testing, backed by BM TRADA and Warringtonfire’s UKAS accreditation.
To support the industry during this critical transition, Warringtonfire is investing £4 million into its flagship fire resistance testing laboratory at its Birchwood Park in Warrington. This will expand its ability to deliver EN testing, classification and technical support services. The 101,000ft2 site will see two additional furnaces installed and operational by the end of 2026, adding to the five furnaces already at the state-of-the-art facility.
Together, Element Materials Technology and Warringtonfire remain committed to supporting clients and the wider construction community as the sector moves fully to EN 13501. With extensive experience in testing, classification and participation in standards development, they continue to provide the technical assurance required to maintain safety and compliance across the built environment. www.bmtrada.com