Transfer slabs under pressure: Failure mechanisms in the spotlight

Guest article written by Katarina Zurkova and Jenna Thomas-Pritchard at DAC Beachcroft

The potential risks posed by transfer slabs, particularly punching shear, have become something of a hot topic for insurers, developers, contractors and design professionals following the Institution of Structural Engineers (IStructE) guidance published in November 2024^[1] aimed at new build design, and the Building Safety Regulator (BSR) alert in December 2025^[2]. Should the alarm bells be ringing? While there are legitimate concerns that require attention, the potential risks need to be kept in perspective.

The information issued by the BSR to principal accountable persons and building owners simply highlights a potential structural safety issue that may affect reinforced concrete buildings constructed with transfer slabs. This reflects the current focus on building safety and the need to identify potential risks. The BSR makes it clear that not all construction with this design feature will have issues and it is not aware of any building collapse caused by punching shear in the UK. The emphasis is on identifying any risks and taking 'proportionate' steps to manage the safety of a building throughout its lifecycle.

The latest guidance, published in July 2026 by the BSR^[3] and IStructE, has provided further clarity on the assessment of existing slabs, including updated Q&A^[4] and interim guidance on the design and assessment of reinforced concrete transfer slabs^[5] for those already carrying out assessments. Detailed guidance for the assessment of existing transfer slabs is expected in mid-2027.

In this article, we consider the potential risks associated with transfer slabs and how structural engineers can demonstrate safe performance, with focus on evidence, verification and proportionate assessment.

What are transfer slabs and what do they do?

Transfer slabs are a key structural element of a building, used as a way of transferring the weight of a building between floors when the layout changes from floor to floor. It allows, for example, a column layout to be supported by a more open configuration below, such as a retail space or a car park. The slab performs as an internal structural bridge, carrying the concentrated forces and transferring the load. Transfer slabs have been used in the UK for over 25 years and are commonly found in residential and mixed-use buildings such as student accommodation or high-rise developments.

Unlike conventional floor slabs, transfer slabs are typically thicker, more heavily reinforced and subject to more complex stress conditions. The most critical regions are often around column heads and areas where the load path shifts direction. These zones require careful design and detailing, particularly where forces are highly concentrated.

The behaviour of these systems is influenced by the complexity of the load paths, particularly where different design approaches are used to transfer vertical forces to foundations or other loadbearing elements. In addition, concrete is susceptible to shrinkage, which can influence how loads are distributed, gradually altering the transfer of forces through the structure over time.

Transfer slab risks

IStructE research and investigations into UK residential developments identified weaknesses in transfer slab design, a complex area, leading to inconsistent industry practice.

To address this gap in knowledge, IStructE issued a guide which aimed to provide a consistent and robust approach for new build structures. While guidance based on current knowledge is welcomed, it has also raised some questions on the adequacy of historic engineering design methods in existing buildings. Having said that, the guide expressly states that non-compliance with the guidance does not necessarily lead to the conclusion that the design of an existing transfer slab is structurally inadequate or statutorily non-compliant. Transfer slabs have a well-established framework for achieving reliable structural performance, supported by recognised design codes and advanced analytical techniques such as finite element modelling. The behaviour of transfer slabs in practice is influenced by a range of factors, including reinforcement positioning, concrete quality, workmanship and site control. Even relatively minor deviations in these areas can have a material impact on performance of the slabs. 

One of the most talked about vulnerabilities is the sensitivity of transfer slabs to 'punching shear' defects. This is where a concentrated load force causes a column to punch through the slab. Unlike more gradual forms of structural behaviour, punching shear can develop without visible indication, placing greater emphasis on careful detailing, adequate reinforcement provision, and appropriate assessment of load distribution. If any of the above are wrong, the vulnerability can quickly turn into a costly issue and potential for a claim.

Transfer slabs are typically concealed within the structure, meaning their condition and performance cannot be readily verified through visual inspection. As a result, confidence in their adequacy depends on the integrity of the design process, the quality of construction, and the availability of supporting records. Demonstrating safe performance therefore requires not only sound calculations, but also appropriate detailing, accurate site execution, and robust verification supported by clear documentation.

Identification and assessment of risk

Identifying and managing potential latent defects is a key focus of the Building Safety Act 2022. The policy of the Act is to engender a more proactive approach, with building owners and accountable parties expected to investigate and address structural risks. In the case of higher‑risk buildings, the existence of a transfer slab may require an update to the building safety case report.  

The BSR's research to establish the level of structural risk associated with transfer slabs is ongoing and further advice is expected. In the meantime, principal accountable persons and building owners are advised by the BSR to take steps to identify whether there is a transfer slab present in the building and to consider seeking professional advice where one exists. Particular attention should be paid to evidence of cracking around column locations, excessive deflection, or cracking within finishes and walls adjacent to transfer slab zones, as these may indicate redistribution of load within the structure.

Importantly, IStructE has confirmed that its November 2024 guidance was developed for new-build design and should not be applied retrospectively to existing buildings. Existing transfer slabs should instead be assessed on their own merits. To support this process, IStructE published interim assessment guidance in 2026 and has established a specialist task force to develop more comprehensive guidance, expected in 2027.

How to evidence safe performance in practice?

A notable development in recent years has been the growing emphasis on verifiable information. Stakeholders increasingly expect clear, auditable evidence covering design, construction and inspection, rather than relying solely on design intent. Where such information is incomplete or unavailable, uncertainty can arise during both technical assessment and commercial decision-making, with risk evaluation reflecting not only the presence of complex structural elements but also the quality and accessibility of the supporting records.

Drawings alone are rarely sufficient. Demonstrating the safe performance of transfer slabs relies on a comprehensive and reliable body of information, including design documentation, construction records and, where necessary, evidence of material quality and workmanship. Gaps in evidence can introduce uncertainty and may necessitate further review or investigation.

Conclusion

Increasingly, the focus is on demonstrating safety through clear and reliable evidence, covering not only design intent but also construction quality and ongoing performance. In practice, this means maintaining good documentation, accurate records and, where appropriate, undertaking proportionate investigation to support informed decision-making.

The independent research commissioned by the BSR does not suggest that transfer slabs are inherently unsafe.  We do not expect a flood of litigation.  Recent focus brings to the forefront potential issues and encourages a more considered and evidence-based approach to understanding the performance of transfer slabs, particularly in existing buildings.

This article has been written by DAC Beachcroft LLP and the opinions and views stated in this article are those of DAC Beachcroft and not Howden Insurance Brokers Limited (“Howden”). Howden is an insurance broker and is not authorised or regulated to advise on the guidance for transfer slabs. Howden shall not (i) owe or accept any duty, responsibility or liability to you or any other person; and (ii) be liable in respect of any loss, damage or expense caused by your or any other party’s reliance on this article.

DAC Beachcroft publications are created on a general basis for information only and do not constitute legal or other professional advice. No liability is accepted to users or third parties for the use of the contents or any errors or inaccuracies therein. Professional advice should always be obtained before applying the information to particular circumstances. For further details please go to www.dacbeachcroft.com/en/gb/about/legal-notice. Please also read our DAC Beachcroft Group privacy policy at www.dacbeachcroft.com/en/gb/about/privacy-policy. By reading this publication you accept that you have read, understood and agree to the terms of this disclaimer. The copyright in this communication is retained by DAC Beachcroft. © DAC Beachcroft

[1] https://www.istructe.org/resources/guidance/design-of-transfer-slabs/

[2] https://www.gov.uk/government/publications/potential-risks-from-transfer-slabs-in-buildings/potential-risks-from-transfer-slabs-in-buildings

[3] https://buildingsafety.campaign.gov.uk/building-safety-regulator-making-buildings-safer/your-home-your-safety/transfer-slabs-residents-guide/

[4] https://www.istructe.org/resources/news/design-and-assessment-of-reinforced-concrete-trans/

[5] https://www.istructe.org/resources/design-and-construction/design-and-assessment-of-reinforced-concrete-trans/istructe-design-assessment-transfer-slabs-july-202.pdf