The BS 476 series is a long-standing, multi-part British Standard. It defines fire testing methods for building materials and structures, primarily focusing on fire resistance and reaction to fire.

The BS 476 series has been a key standard in the UK for evaluating the performance of construction materials when exposed to fire.

The background of BS 476

First published in 1932 to provide a testing method for assessing the fire resistance of building materials, over the years, the standard expanded into multiple parts, covering various aspects of fire performance, including ignition resistance, flame spread, and heat release. The BS 476 series evolved in response to major fire incidents, changing regulatory needs, and advancements in fire science, and came to be seen as cutting-edge.

The 1970s and 1980s saw significant updates, especially with the publication of Part 7 (1971) and Parts 20 to 24 (1987). Those updates introduced more precise methods for testing spread of flame and fire resistance respectively. Several revisions were made to align with the evolving safety expectations set by the Building Regulations of England and Wales.

By the late 1990s and early 2000s, BS 476 began to be gradually replaced or supplemented by European standards (the BS EN 13501 series of classification standards and relevant test standards) as the UK moved toward European fire testing procedures.

Key parts of the BS 476 series

The BS 476 series is divided into multiple parts, each focusing on a different fire performance characteristic. Key parts include:

• BS 476-4: Non-combustibility test for materials.

• BS 476-6: Fire propagation test, assessing how much heat is released by a material.

• BS 476-7: Surface spread of flame classification (Classes 1 to 4).

• BS 476-11: Ignitability testing.

• BS 476-20 to 24: Fire resistance tests for structures, including load-bearing walls, floors, ceilings, and fire doors.

A change of status

The biggest change to the status of BS 476 occurred in the late 2000s, when a number of parts were proposed for withdrawal following the publication of superseding British adoptions of European standards.

In response, BSI received representations from industry expressing concern at the withdrawal, although there was recognition that, through its obligations as a member of CEN, withdrawal of conflicting national standards is a requirement.

However, there was concern the status of 'withdrawn' could be interpreted to mean that the affected parts could no longer be used. Those parts were still referred to in the government's guidance document Approved Document B (ADB) and were also used extensively in other countries outside of the EU with an historic link to the United Kingdom.

BSI, therefore, withdrew the parts as required (the withdrawn documents are still available to purchase on BSI Knowledge), but took the step of amending the foreword of each part to state:

This standard has been superseded by the current BS EN XXX, but it has been retained based on legitimate need for the standards within non-EU markets.

As BS 476 was a conflicting national standard under CEN rules, updating and revising the parts wasn’t possible, although industry still had the option to continue using them instead of the relevant BS ENs, where appropriate.

Transitioning to European fire testing standards in the UK

Although the UK has now left the European Union, BS 476 has not been reinstated as the primary fire testing standard. This is due to BSI, as the UK’s national standards body (NSB), remaining a full member of CEN-CENELEC, which is an organization separate from the European Union. BSI therefore participates in European standardization on the same basis as before Brexit.

UK building regulations have previously been amended to align with EN 13501-1 for reaction to fire classification, requiring materials to be classified under the Euroclass system (A1 to F) rather than the traditional BS 476 classifications . However, some UK-specific applications, such as in refurbishment projects or legacy systems, were still able to reference BS 476 tests.

One area that the inquiry into the 2017 Grenfell Tower Fire focussed on was the inclusion in building regulation guidance of national classification system, using BS 476, and the European system, using the EN.

Following a consultation undertaken in 2024, the Ministry of Housing, Communities, and Local Government (MHCLG) has announced the removal of the relevant parts of the BS 476 series from the statutory guidance to the building regulations Approved Document B: Fire Safety. This decision reflects a shift towards alternative standards and does not imply any fault or wrongdoing by BSI, nor does it suggest that BSI contributed to the causes of past fires.

The first tranche of standards covering reaction to fire will be removed 2nd March 2025, with a second tranche covering fire resistance being removed 2nd September 2029.

Those being removed on 2nd March 2025 are:

• BS 476-3 - [see below]

• BS 476-6 – superseded by BS EN 13823

• BS 476-7 – superseded by BS EN 13823

• BS 476-11 – superseded by BS EN ISO 1182

Those being removed on 2 September 2029 are:

• BS 476-8 – superseded by BS EN 1634-1:2014 A1:2018

• BS 476-20 – superseded by BS EN 1363-1:2020, BS EN 1363-2:1999

• BS 476-21 – superseded by BS EN 1365-1:2012, BS EN 1365-2:2014, BS EN 1365-3:2000, BS EN 1365-4:1999

• BS 476-22 – superseded by BS EN 1634-1:2014 A1:2018

• BS 476-23 – superseded by BS EN 1634-1:2014 A1:2018

• BS 476-24 – superseded by BS EN 1366-1:2014 A1:2020, BS EN 1366-8, BS EN 1366-9

• BS 476-31.1 – superseded by BS EN 1634-3:2004

In response to this change, BSI will be updating BSI Knowledge to make it clear the affected parts have been withdrawn, with adjustments to the statement in the foreword to:

This standard has been superseded by the current BS EN XXX and will be withdrawn on 2 September 2029.

An exception to this is BS 476-3, which will remain as a current standard. This is because it has not yet been superseded by an BS EN although work is ongoing within CEN/TC 127 to convert CEN/TS 1187 to a full EN.