BS 476 and EN 13501: What you need to know

On 2nd September 2024, nearly 18 months after the consultation closed, the government has confirmed that the National Classes fire testing standards will be withdrawn from 'Approved Document B' in favour of the EN 13501 series of European classification standards. The statement was made by Building Safety Minister Rushanara Ali alongside other building safety updates and can be read in full on the UK Parliament website.

Ever since the consultation was launched, the discussions in the construction product industry have remained heated with many manufacturers asking how the BS 476 series differs from the EN classification system and what level of investment in future EN test programmes will be required to maintain their current BS 476 scope.

Manufacturers have also voiced concerns about the time required to transition to the European classification system, given the amount of testing that may be required and whether there is sufficient testing capacity within the UK to cope with the potential demand.

But what exactly is BS 476, what are the key differences compared with the EN classification system, and what should construction product manufacturers, particularly those currently relying on BS 476 evidence, do to prepare now that the direction of travel has been confirmed?

Peter Barker, Technical Policy Manager at Element Materials Technology, explains more.

BS 476 Series of Standards – What is it?

The BS 476 standard was first published in 1932 and was initially a single standard that set out standardised conditions against which the fire performance of construction elements and building components could be evaluated. The standard covered incombustibility and non-inflammability of construction products (i.e. the behaviour of construction products in the early stages of fire, focussing on fire spread and growth – now termed reaction to fire) and resistance to fire (i.e. the behaviour of construction products in the later stages of fire, focussing on structure and containment). In the following decades, the BS 476 standard was split into different parts, with each part focussing on a specific aspect of fire performance or type of construction product. For example, the BS 476: Part 22 standard was developed specifically for non-load-bearing elements of construction. This standard, in conjunction with the BS 476: Part 20 standard (the standard that sets out the general requirements for fire resistance tests), is used to establish the performance of construction products such as doorsets and partitions. 

The BS 476 series of standards has been developed by UK industry experts within BSI over many years, with the standards being periodically revised and updated to make sure they reflect advancements and knowledge from a wide field of expertise within the construction and fire safety industries. The revision and update of the BS 476 series of standards began to slow in the early 1990s with the last standard in the series being technically reviewed in 2009. The primary reason for the reduction in revising the BS 476 series of standards was the development of the EN series of standards to meet the regulatory objectives of the E.U. single market.

The BS 476 series of standards has been successfully used as benchmark standards for establishing the fire performance of construction products in the U.K. for decades. However, the series also sees some international use and has been adopted as an acceptable means for demonstrating the performance of construction products to meet the requirements of building codes and regulations in other parts of the world, such as Hong Kong and the United Arab Emirates. Indeed, one of the reasons for retaining the BS 476 series of standards was for use in other territories outside the E.U.

The BS 476 series of test standards sets out the test conditions and criteria used to evaluate the performance of construction products in standardised test conditions. The output from the testing is conveyed in a test report, which refers to the test method and conditions, and provides a detailed description of the tested product and the performance achieved. The test report communicates the results of the test, which provides a benchmark against which similar products can be compared and allows the product to be considered for use within the building according to the relevant regulatory requirements. The test report does not provide any extension to scope beyond the product tested. Any variation to the tested scope would either need to be accepted by the Authority Having Jurisdiction (AHJ) or assessed by a test laboratory with the necessary level of expertise.

Technical assessments in the UK use expert judgement to provide a scope of application using sufficient and relevant test evidence for the design. These are prepared by individuals with the relevant level of knowledge and competency of the product and its behaviour in fire test conditions. Assessing bodies in the UK follow the principles and guidance set out in the Passive Fire Protection Forum (PFPF) guide to undertaking technical assessments of construction products, which provides information on the process and the competency requirements for the product assessors responsible for preparing and checking the reports.

It is important to understand that the approach used for extending the scope of tested designs using evidence generated to the BS 476 series of test standards is fundamentally different to that used within the EN classification system, as it helps explain why a transition to the EN classification standards is not as simple as re-testing products to a different test method.

EN 13501 Series of Standards – What is it?

The EN 13501 series of classification standards were developed by the European Committee for Standardization (CEN) in response to the mandates issued by the European Commission outlining a requirement for a harmonised system of testing and classifying construction products that could be used to meet the requirements of the Construction Products Directive (CPD). The primary aim of the CPD was to remove barriers to trade and create a common technical language to facilitate the movement of products throughout the E.U. The CPD was replaced by the Construction Products Regulation (CPR) in 2011, which uses the same supporting classification system as that originally developed for the CPD.

The classification system relies on a basic philosophy: having common test methods that can be used to establish the performance of a construction product, where a specific characteristic of performance can be classified, declared by the manufacturer placing the product on the single market and therefore recognised by any member state within the single market of the E.U.

Many of the countries within the E.U. already had their own national test methods for establishing the fire performance characteristics of construction products, prior to the introduction of the CPD and development of the EN classification system. Experts from across Europe were nominated by their respective National Standardization Bodies (NSBs) to work together within CEN to develop standards that met the mandates issued by the European Commission and support the functioning of the European single market. CEN continues to provide a platform for the development of European Standards and other technical documents in relation to various kinds of products, materials, services and processes and brings together the NSBs of 34 European countries.

Given the objectives of creating a harmonised system for establishing the performance of construction products that could be recognised across multiple territories, the mandates from the European Commission not only asked for a single test method and classification system but also a set of rules for extending the scope of the tested designs. For fire performance, this led to the creation of Direct Application (DIAP) and Extended Application (EXAP) rules, which are written into the test standards, harmonised technical specifications (product standards and European Assessment Documents) or contained within separate standards. DIAP/EXAP rules are being continually developed and revised by the relevant working groups in CEN with consultation and feedback via NSBs’ mirror committees as part of the enquiry process. The DIAP/EXAP rules are used to extend the scope of the tested designs, which can then be classified using the relevant part of the EN 13501 series of standards.

Herein lies the key differences between establishing the performance of construction products using the BS 476 series of standards and the EN classification system. The extension to scope under BS 476 is based on the expertise of the laboratory, but to generate a classification using the EN 13501 series of standards, a set of standardized rules is used. However, it is worth mentioning that, even though the DIAP/EXAP approach uses rules set out in the standards, applying the rules correctly requires skill and expertise on the part of the laboratory preparing the classification, particularly where more than one performance characteristic is being considered for the product.

Although the EN classification system for construction products was developed to support the functioning of the single market under the CPR, the EN classification system 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.

Why is this change being considered?

Since the introduction of the EN classification system, both the BS 476 series of standards and the EN standards have been stated in Approved Document B as an acceptable means for demonstrating the performance of construction products. According to the explanation in the government consultation, and statement made by the government on 2nd September 2024, the withdrawal of the BS 476 series from Approved Document B is a recognition of a long-standing ambition by the UK Government to have a single standardisation system supporting the performance of construction products. The government has also stated that the withdrawal of BS 476 implements the recommendation made in the Hackitt Report, for a clearer, transparent and effective safety regime. The withdrawal of BS 476 is not effective immediately; the government is providing industry with a transition period of 6 months for reaction to fire and 5 years for resistance to fire.

The removal of BS 476 from Approved Document B is complicated as the suite of standards spans both reaction to fire and resistance to fire and covers many different construction products. For some manufacturers, who had a regulatory driver to test and classify using the EN standards, the transition is relatively straightforward as they will have generated test evidence and classifications to the appropriate EN standards. For other sectors of the construction industry, who have continued to test using the BS 476 series of standards, it could be more challenging.

The key challenges facing any construction product manufacturer moving from a BS 476 suite of evidence to the EN classification system are outlined below:

1. BS 476 test evidence cannot be used to generate a classification using the EN 13501 series of standards. The EN classification system communicates the performance characteristics based on the results of the testing to the specific EN test methods.
2. The EN classification system uses DIAP and EXAP rules to extend the scope of the tested designs. A test programme based on the BS 476 series of standards will not generate the same scope if it were to be repeated using the EN test standards and the scope extended using the relevant DIAP/EXAP rules. 
3. Depending on the manufacturer’s product range, there could be a significant number of tests required to classify their current scope to the EN standards. Furthermore, the evidence will need to be generated in a relatively short space of time, with other manufacturers' test programmes being run concurrently. 
4. Products may need to be redesigned to provide the required level of performance against the EN test method. There are differences between the BS 476 standards and the equivalent EN methods, which can place different demands on the product in fire test conditions. This does not automatically mean the product previously tested to the BS 476 standard was not suitable for its end-use application within a building, only that the conditions of the EN test method place different demands on the product that may need to be addressed by product redesign to achieve the necessary level of performance.

What can manufacturers do to prepare for any potential change?

The government has now clearly stated the direction of travel with respect to the future of BS 476 in England and given the period for manufacturers to transition to the EN classification system. 

Ultimately, it is up to the manufacturer when they choose to embark on an EN test programme. However, timing will be critical given the challenges outlined above, as there is a limited amount of time in terms of the transition period and there is likely to be increased demand from the construction industry for products to be tested, classified and certified using the EN classification system. 

For some manufacturers, it may be demanding to cover their complete scope of products to the EN classification system in one hit. Manufacturers will be tempted to replicate existing scopes in their entirety, which may lead to large and complex test programmes, and therefore take longer to complete. Many manufacturers have spent a long time generating the necessary evidence to cover the full range of designs being offered under the BS 476 regime. If a manufacturer feels it is necessary to cover their existing scope, then it pays to start the process as soon as possible, as not only will the evidence and supporting documentation such as EXAPs and classification reports take time to complete, but there may also be some product redesign required as explained above. 

As the EN classification system is rule-based, it is helpful for manufacturers to detail the scope of the product family or product range that they want to offer to the market and provide this information to their chosen test laboratory. This allows test programmes to be reverse engineered according to the DIAP or EXAP rules for that product. The process of reverse engineering using DIAP and EXAP rules is complex, particularly when more than one performance characteristic is being evaluated for a product, and a manufacturer will want to use a test laboratory that has experience in testing to the EN test methods and writing EXAP and classification reports. Warringtonfire has over 20 engaged experts on various working groups within CEN that are responsible for the development of EN test, EXAP and classification standards across many different types of products. Warringtonfire has been testing to the different EN test methods since their inception (over 20+ years) and has a deep understanding of how DIAP rules and EXAP rules are applied to generate a scope that can be used to provide a classification using the EN 13501 series of standards. 

After the consultation was launched, one of the concerns raised by manufacturers and highlighted in the Independent Review of the Construction Products Testing Regime, prepared by Paul Morrell OBE (Chair) and Anneliese Day KC, was that of test laboratory capacity. Warringtonfire has three UKAS-accredited facilities within the UK and a BELAC-accredited facility in Belgium that can provide EN testing to many different methods, for multiple construction products in the field of reaction and resistance to fire. Furthermore, in response to the demand from industry for additional capacity, Warringtonfire has invested in a brand-new 101,000sqft site in Warrington. Construction of the $30m world-leading facility is currently underway and it is due to open in early 2025. 

The new facility is designed to increase efficiency in the testing process and meet the potential for increased demand; it represents an almost 80% expansion in size over Warringtonfire’s existing facility in the region and is expected to triple its testing capacity in the medium term.

In addition to increasing testing capacity, Warringtonfire continues to add to its technical and certification expertise by attracting experienced technical experts from industry but also training and developing talent in-house through bespoke training and graduate schemes. 

The construction product industry will continue to experience changes to the regulatory landscape, which will understandably pose challenges to manufacturers and other stakeholders working in the industry. The announcement from government to withdraw the BS 476 series from Approved Document B in favour of the EN classification system (EN 13501 series) is undoubtedly one of the largest changes in policy with respect to construction products and fire safety in decades. Warringtonfire is committed to supporting our clients and the wider industry during this transition period. We are accredited to the relevant European standards, have long-standing experience preparing extended application reports and classifying construction products using the EN 13501 series of standards and can continue to provide the required services for testing and certifying manufacturers’ construction products.

For more about Warringtonfire and its new Birchwood Park laboratory, or to book for 2025, please click here.