Insights
05 Feb 2026
What is the latest news on transfer slabs?
In December 2025, the Building Safety Regulator (BSR) publicly raised concerns over a structural safety issue that can affect buildings constructed with transfer slabs.
A letter was issued to principal accountable persons and building owners that drew attention to potential risks that have been identified with reinforced concrete multi-storey buildings that include transfer slabs.
The concerns centre upon a lack of clear methodology for the design of transfer slabs and the propensity for collapse, due to overstressed transfer zones cracking and, at worst, partial collapse.
In light of this, Hollis director Richard Hunt– head of our Building Forensics service – sat down with Andrew Ruck, director at Civic, to answer some key questions on this topic.
What exactly is a transfer slab, and why are they commonly used in multi-storey buildings?
A transfer slab is a thick, heavily reinforced concrete floor that acts as a bridge to support columns from upper floors that don’t align with columns below.
They are often seen in mixed use developments, including residential buildings with car parks at ground level, and have become more common over the last 25 years.
What triggered the recent alert from the BSR regarding transfer slabs?
In 2024, an engineer used Collaborative Reporting for Safer Structures (CROSS) – the Institution of Structural Engineers’ (IStructE) confidential reporting system – to flag missed checks in some transfer slab designs.
This prompted IStructE’s guidance in November 2024 and CROSS professional guidance soon after.
The specific concern is punching shear at out-of-line columns, where overstressed transfer zones can crack and, at worst, partially collapse.
Have there been any failures associated with this?
No, there is currently no evidence of a UK collapse linked to this issue, although the government notes concern about a failure mechanism that could cause partial collapse if present.
There was a tribunal case in late 2025 to order investigation, temporary propping and permanent remediation after cracking was observed around support columns and concerns were raised about the strength of first-floor slabs at Wotton Court in London.
A later engineering report for the case said the most likely cause was a punching shear failure, with potentially severe consequences, including partial collapse.
What are the early warning signs of distress to watch for?
Most buildings with transfer slabs will perform as intended. When distress does occur, one early sign may be cracking to the slab soffit, local to column locations bearing on the slab.
Visible cracking merits urgent engineering review.
Which building types and construction eras are most at risk?
The present focus is on reinforced-concrete frames, particularly modern mixed-use buildings in which there are changes to column grids between storeys.
Industry discussion has centred on buildings from roughly the last two to three decades, when complex mixed-use forms and software-led analysis became more prevalent. Some practitioners have become heavily reliant on software, potentially overlooking critical checks.
How can asset owners and principal accountable persons assess whether their buildings are affected?
Start with a proportionate, desk-based review:
Identify whether the structure includes reinforced-concrete and if there are transfer slabs. Use as-built drawings, specifications and calculation packs as your first port of call. Think about changes of use between levels and / or areas where there are large column-free spaces with floors above.
If your building is a higher-risk building (HRB), it should have had a safety case report completed in accordance with the Building Safety Act (BSA). This would have included a structural assessment, and the presence of transfer slabs and associated issues should have been considered and assessed.
If signs of distress are detected, what should the immediate next steps be?
Firstly, don’t panic. There is currently limited evidence to suggest this is a really significant issue.
That said, if you are concerned about this issue, we would recommend you proceed as follows:
Establish whether any of your buildings incorporate reinforced concrete transfer slab designs. This could be via as-built documentation, recent surveys or via a targeted site inspection by a Chartered Structural Engineer, or a Chartered Surveyor.
If transfer slabs are found to be present, consider having an inspection completed by a Chartered Surveyor or a Chartered Structural Engineer to look at the design in further detail and to identify any signs of visible defects that could be suggestive of a design defect – primarily cracking to soffits beneath columns. They will be able to advise upon a suitable remedial scheme.
From your experience, what practical challenges arise when retrofitting or remediating transfer-slab systems?
Records – including calculations and reinforced concrete detailing – can’t always be found and aren’t necessarily adequate if they are.
If there is a punching shear problem, adding steel plates or carbon fibre reinforcement might be considered.
In such cases, typical challenges include access to soffits in occupied buildings, working over live car parks or retail units, service diversions, headroom constraints, permits and stakeholder communications.
Programme impacts and night-time working are common. Early planning and clear sequencing mitigate disruption.
Firms like Hollis can offer real, practical support to duty holders by bringing in experience from similar projects and close ties with engineers who know the regulations and challenges inside out. That means they’re not just ticking boxes but helping make decisions that work for each individual project.
What role can firms like Hollis play for duty holders?
Because they’ve seen what works (and what doesn’t), they can help duty holders find answers quickly, deal with unexpected issues, and stay on track.
Anything else to add?
While the issue has been highlighted, it is not on the same scale as the RAAC crisis.
The BSR commissioned independent research in late 2024 to establish the level of structural risk associated with transfer slabs and consulted the Building Advisory Committee (BAC).
They are currently working with industry partners and the BAC to better understand how the risk can be identified and proportionately managed in existing buildings.
Current evidence suggests a need for awareness and proportionate due diligence, not wholesale investigation of every concrete frame.
Expect further technical updates as research and professional guidance evolve.
To find out more about our Building Forensics offering, visit: https://www.hollisglobal.com/what-we-do/services/building-forensics/
Sources:
- https://assets.publishing.service.gov.uk/media/69467aeb72075a1d4a5089a7/251219_J_Sheftel_Wotton_Court_Decision.pdf
- Building Safety Regulator, “Potential risks from transfer slabs in buildings,” GOV.UK, 2025. (GOV.UK)
- Institution of Structural Engineers, Design of transfer slabs, November 2024. (istructe.org)
- CROSS-UK, “Punching shear assessments of flat slabs supporting out-of-line columns,” 16 December 2024; and professional guidance summary, May 2025. (cross-safety.org)
- GOV.UK, “Preparing a safety case report,” guidance for principal accountable persons, updated page. (GOV.UK)
- RICS, “Transfer slabs in buildings: advice and FAQs,” January 2026. (RICS)