History of BS 476 and Its Application to Fire Doors

History of BS 476 and Its Application to Fire Doors

Origins of BS 476 as a Fire Resistance Standard

BS 476 is a long-standing British Standard for fire testing of building materials and structures. It was first published in 1932 as a single standard to evaluate both the early-stage flammability (reaction to fire) and later-stage fire resistance of construction elements . Over subsequent decades, this standard was expanded into a series of parts, each addressing specific fire performance aspects (e.g. ignition, flame spread, heat release) . By mid-20th century (around the late 1940s), BS 476 had become the cornerstone of UK fire testing, providing standardized methods to grade how materials and assemblies behave in fire . These early versions laid the groundwork for assessing structural fire resistance in buildings.

Key Revisions and Development

Major updates to BS 476 occurred in the 1970s and 1980s to keep pace with advancing fire safety science and regulatory needs . Notably:

• 1971: BS 476 Part 7 was introduced to classify surface spread of flame on materials (Classes 1–4) . This addressed how quickly fire can spread across surfaces, an important factor in building design.

• 1972: BS 476 Part 8 was published as a comprehensive fire resistance test for building elements. This was a pivotal standard that, for the first time, provided a unified method to test the fire endurance of walls, floors, and door assemblies. Part 8:1972 became the basis for fire door testing in the UK through the 1970s and early 1980s.

• 1987: A major revision split and improved the fire resistance test methods. BS 476 Parts 20–24 (1987) were introduced as a more precise, “technically superior” update to Part 8 . In particular, Part 20 defined general principles for fire resistance tests, and Parts 21–24 covered specific elements (loadbearing structures, non-loadbearing elements, contributions of components, ducts, etc.) . This 1987 overhaul aligned BS 476 with modern testing practices and the evolving Building Regulations of that era . After this point, BS 476 Part 8:1972 was withdrawn in favor of the Part 20 series for any new fire resistance testing . (Tests to Part 8 already done remained valid, as noted below.)

BS 476 and Fire Doors in UK Regulations

Fire doors became explicitly covered under BS 476’s fire resistance tests starting in the 1970s. BS 476 Part 8 (1972) included methods to test door assemblies for fire endurance, and it was referenced in guidance of the time for certifying fire doors. In fact, UK Building Regulations (e.g. Approved Document B) allowed fire doors tested to Part 8:1972 to remain acceptable for installations completed before the late 1980s .

With the 1987 update, BS 476 Part 22:1987 was dedicated to non-loadbearing elements of construction – including complete door sets (fire doors) and partitions . Part 22 (used together with Part 20’s general criteria) became the standard fire door test method moving forward. In practical terms, 1987 marks when BS 476 specifically became the applicable standard for fire doors under UK regulations, supplanting the old Part 8 test. From 1988 onward, new fire door tests had to use BS 476 Parts 20 & 22, while doors tested earlier to Part 8 were grandfathered as acceptable . This ensured continuity – a door certified under the old standard didn’t “become obsolete” simply because the standard was updated . The classifications derived from BS 476 (e.g. FD30, FD60 indicating 30 or 60 minutes fire resistance) were embedded in building codes for fire door requirements. Key points in this history include:

• BS 476: Part 8 (1972): First modern fire door test in BS 476; used through the 70s/80s for certifying fire doors.

• BS 476: Part 22 (1987): Updated method for fire doors (non-loadbearing elements) in conjunction with Part 20; became the primary referenced standard in UK regulations for fire door testing from late 1980s onward .

• UK Building Regulations (Approved Document B) explicitly recognized Part 22 tests for fire doors, while also accepting existing Part 8 test evidence for older doors pre-1988 . This transition ensured that the introduction of Part 22 in 1987 directly tied BS 476 to fire door compliance in regulation.

Transition to BS EN 1634 and Modern Standards

From the late 1990s, the UK began moving toward European fire testing standards for harmonization . The modern counterpart for fire door testing is BS EN 1634-1, a European standard that evaluates the fire resistance of door and shutter assemblies (including door sets) under a common EU framework.

BS EN 1634-1 was first published around 1999–2000 and has since been updated (e.g. 2008, 2014+A1:2018). It is broadly equivalent in scope to BS 476 Part 22 but is part of the EN standards suite used across Europe. In UK practice, BS 476-22 and EN 1634-1 have run in parallel for some time – both are currently accepted test methods for demonstrating fire door performance . However, EN 1634-1 is increasingly favored as it aligns with international (European) classification systems (EN 13501) and is considered more rigorous in certain aspects. For example, EN 1634-1 uses slightly insulated plate thermocouples and positions the furnace pressure regime differently (lower “neutral pressure plane”), which can make the test more stringent on the door’s performance . These differences mean EN 1634-1 can be a tougher test, prompting many manufacturers to ensure additional protections (like intumescent seals on hardware) when testing to EN 1634-1 .

In terms of standard status and regulation: BS 476 Part 22 is now technically superseded by BS EN 1634-1:2014+A1:2018 as the state-of-the-art test for fire doors . The British Standards Institution, as a CEN member, must withdraw conflicting national standards in favor of EN standards. Indeed, the UK government has signaled the phasing out of national BS 476 “Class” tests in Approved Document B. Recent policy announcements (post-Grenfell) indicate that the BS 476 series references will be removed from official guidance in stages – with reaction-to-fire parts removed by 2025 and fire-resistance parts (including BS 476-22) by 2029 . This means that in the future, only BS EN 1634-1 (and related EN standards) will be used for fire door compliance testing in the UK.

For now, both standards are still recognized: a fire door can be rated via BS 476-22 (national classification) or EN 1634-1 (European classification), and an FD30/FD60 door tested to BS 476 is equivalent to an E30/E60 door under EN 1634-1 in terms of integrity performance. The trend, however, is that BS 476’s role is historical and transitional, while BS EN 1634-1 is the modern benchmark. In summary, BS 476 laid the foundation for fire resistance testing (with roots back to 1932 and specific fire door tests since the 1970s), and its legacy carries on through contemporary standards like BS EN 1634-1 that continue to evolve fire door testing for today’s safety requirements .

Sources:

• BSI, “The changing status of the BS 476 standard series: A summary.” (Feb 2025) – Historical overview of BS 476 (first published 1932) and its evolution .

• Warringtonfire, “BS 476 and EN 13501: What you need to know.” – Confirms BS 476’s 1932 origin and explains the purpose of Parts 20 & 22 for doorsets .

• Health & Safety Forums – Discussion referencing Approved Document B: fire doors tested to BS 476 Part 8:1972 remained acceptable if installed before 1988 . Highlights the 1987 shift to Part 22 in regulations.

• Fire Industry Magazine (AIJ), “Proposed removal of BS 476:22 for fire doors…” (Sep 2023) – Notes that BS 476:22 (in place since 1987) has seen no major updates in decades, and contrasts it with EN 1634-1’s methodology .

• BSI/UK Gov – Announcement of withdrawal of BS 476 parts from Approved Doc B in favor of EN standards . (BS 476-22 to be replaced by BS EN 1634-1 by 2029 in official guidance).