Lead Author – Toby Maclean, Allt Environmental & independent specialist advisor to Woodknowledge Wales
June 2026
Woodknowledge Wales welcomes the Government’s continued focus on improving fire safety following the Grenfell Tower tragedy. However, we are concerned that the proposed amendments to Approved Document B (ADB) will have significant unintended consequences and increase confusion rather than improve clarity.
Approved Document B has historically been used as prescriptive guidance for common building situations, but it was not developed as a complete design methodology for large or complex buildings including those constructed from combustible structural materials.
As the document notes, “the guidance itself recognises that it is directed towards common building situations” and that its assumptions do not readily extend to “tall, large or complex buildings in which the structure contributes as a source of fuel”. The consultation appears to acknowledge these limitations but does so indirectly, without providing a clear alternative framework for buildings that fall outside ADB’s prescriptive scope.
The proposed changes to Requirements B3 (internal fire spread – structure) and B4 (external fire spread) lack sufficient explanation of their evidential basis, risk rationale and intended performance outcomes. As a result, they may inadvertently:
- restrict some construction types without transparent justification,
- allow unsafe designs to remain technically compliant, and
- increase reliance on bespoke fire engineering in situations where clearer guidance would suffice.
The central issue is not whether greater stringency is warranted, but whether the regulatory system provides clarity, coherence and a consistent methodology. The current drafting introduces “new terminology and measurement approaches that are inconsistent with those defined elsewhere in the regulatory framework” , lacks clarity in its intended application, and fails to articulate the fire safety objectives underpinning key thresholds and exclusions.
The proposed changes to ADB appear to be attempting to define some of the limitations of ADB but do so in an oblique manner and do not provide an alternative framework.
A more transparent, risk‑based and performance‑oriented approach—supported by clear definitions, aligned height measurements, and explicit criteria for when ADB does and does not apply—would better support both innovation and safety.
We therefore recommend that Government:
- Reconsider the current drafting of the proposed amendments to ADB.
- Clearly define, within ADB itself, the categories of buildings and construction types considered to fall outside “common building situations”, including explicit reference to combustible structural systems, heights or storeys, use types, and compartmentation as relevant.
- Publish, alongside future amendments, a clear statement of fire safety objectives for each major provision, including the risk being addressed, the assumed fire scenario(s) and the expected performance outcome.
- Along with the above, develop explicit performance expectations for buildings that fall outside the scope of prescriptive guidance. This would allow professional to operate outside the limited guidance of ADB under clear criteria.
- Align terminology and measurement methodologies across the Building Regulations, Approved Documents, the Building Safety Act and other standards such as BS9991.
- Improve transparency regarding the technical development of future fire safety guidance.
These changes would improve confidence in the regulatory system, and improve clarity, which in turn would lead to improved fire safety.
To receive a pdf copy of our full response, please contact Woodknowledge Wales.
