Changes to Approved Document B – marking the transition from BS 476 to BS EN 13501
27th November 2024
The Government has announced three significant amendments to Approved Document B: Fire Safety (Volumes 1 and 2), which will be introduced in stages, with the first changes taking effect from 2 March 2025. These amendments are part of an ongoing effort to align UK fire safety standards with European practices, making compliance more rigorous while also enhancing safety for building occupants.
Currently Approved Document B operates a dual testing system referencing both the European Standards and National Classes (BS.476) series of tests for construction products relating to “reaction to fire” and “fire resistance”. Removing references to the National Classes (BS.476) from the Annex of Approved Document B will complete a move to a single testing system under BS EN 13501 series in England. UK Government will be removing references to the National Classes (BS.476) from Approved Document B, leaving the BS EN standard as the sole specification route.
This will enhance fire protection by simplifying the specification routes within Approved Document B and utilising the more robust, periodically reviewed, and internationally recognised approach within the BS EN 13501 series. A full transition to this standard will enable government to use updated standards as compared with the current national ones which cannot be updated, thereby producing new buildings which look to the future rather than the past.
From 2 March 2025
The first changes taking effect from 2 March 2025 introduces updated guidance on several fronts. It will first establish new requirements for installing sprinklers in care homes, aiming to enhance fire safety protections for vulnerable populations. This may impact trussed rafter and metal web designs in such buildings through increased pipework and potentially additional water storage tanks in the loft space.
In addition, this amendment will remove references to BS 476 regarding the national reaction to fire classifications in materials such as the terms Class O or Class 1 and in roof coverings such as Class AA or Class CC. From this date only BS EN 13501 classifications for reaction to fire will be used going forward. The shift to BS EN 13501 marks a substantial update, as it will require materials to meet more stringent fire safety testing and classification, ensuring uniformity across the industry.
It is therefore good to know that wood products such as trussed rafters and metal web that are CE/UKCA marked to a harmonised standard (or ETA) and need Reaction to Fire classification will already be classified with BS EN 13501 designations such as D-s2, d0. These products already comply with the new Building Regulation requirements and need take no further action.
These classifications will have been in place since the harmonised standard BS EN 14250 replaced BS.5268 part3. Therefore TRA members should take pride in the fact we have been meeting this “new” building regulation requirement since we produced our first Declarations of Performance back in 2013.
Following the Government announcement a number of larger House Builders have circulated questionnaires asking their suppliers to confirm that all products supplied will be compliant by 2 March 2025. For TRA members the answer is simple “This change in standards is applicable to the products you procure from us and they are currently compliant.”
The move away from national fire classifications for Roofs will not impact TRA members directly but those undertaking full roof design should ensure the chosen roof coverings meet the BS EN classes below. However, we suspect like TRA members many manufacturers of roof coverings will have made the change long ago.
| Required from 2 March 2025 BS EN 13501- 5 | BS.476 National Fire Classifications – Roofs |
| BROOF(t4) | AA, AB or AC |
| CROOF(t4) | BA, BB or BC |
| DROOF(t4) | CA, CB or CC |
| EROOF (t4) | AD, BD or CD |
| FROOF (t4) | DA, DB, DC or DD |
From 30 September 2026
The second amendment booklet is scheduled for implementation on 30 September 2026 however as the changes only apply to buildings over 18m they are not directly relevant to TRA members.
From 2 September 2029
The final amendment in this series, coming into effect on 2 September 2029, marks the complete phase-out of BS 476 by removing all references in part B of the Building Regulations to national fire resistance classifications. At this point, BS EN 13501 will be the sole recognised standard for fire safety classification within Approved Document B. This means that any reference to national fire resistance tests under BS 476 will be obsolete, and all construction materials used in fire-critical applications must meet the BS EN 13501 classifications for both reaction to fire and fire resistance.
Fire Resistance testing and classification is undertaken on construction elements such as walls, floors or ceilings rather than individual construction products. For some sectors such as the manufacturers of fire door assembles the five year transition period is essential to allow sufficient time to undertake the vast fire test programme which is necessary for the move from BS.476 to BS EN 13501.
As individual construction products trussed rafters and metal web are not required to undertake fire resistance testing or classification. However the generic fire resistance testing of floors ceilings and party wall spandrels carried out by the Systems, TRA and Fermacell will all be subject to these “new” requirements. Once again it is good to know that all the testing carried out on behalf of TRA members anticipated this change in requirements and is already meeting the testing and classifications of BS EN 13501.
To learn more about the amendments in Part B detail, members can review the full documents online: Amendments to Approved Document B: Fire safety.
