Punching shear: potential structural safety issues concerning transfer slabs
May 2026The Building Safety Regulator (BSR) has recently issued warnings in relation to a potential structural safety issue affecting reinforced concrete buildings which incorporate transfer slabs. These warnings follow concerns within the engineering profession that certain historical design approaches may, in certain circumstances, have underestimated the risk of brittle structural failure, most notably as a result of punching shear.
The BSR, together with relevant professional bodies, has emphasised that transfer slabs are not inherently unsafe. However, the regulatory response represents a significant development for the construction, property and insurance sectors, particularly given the residential component of many buildings in which transfer slabs are present.
Transfer slabs: definition and use
A transfer slab is a horizontal reinforced concrete structural element designed to redistribute vertical loads where the structural load-bearing arrangement above does not align with that below (for example where columns do not align with supporting columns or walls directly beneath them). Transfer slabs have been a common feature of UK construction for over 25 years and are most frequently used in high-rise and mixed-use developments. Their use provides architectural flexibility, and they are commonly employed to form podium levels, allowing residential units to be constructed above open-plan parking, commercial or amenity space below, where a different column grid is required.
Transfer slabs can be designed as flat slabs, typically eliminating the transfer beams. While this approach can reduce the cost and complexity of temporary works to form the slab, it also places greater reliance on slab strength and reinforcement as well as column and associated up/down stand design to achieve adequate structural performance. These arrangements have attracted increased professional scrutiny, as their apparent simplicity can obscure more complex structural behaviour, particularly in relation to load transfer and punching shear capacity.
Punching shear and structural behaviour
The current concern centres on the risk of punching shear; a brittle failure mechanism which arises from the downward load imposed by the structure above a transfer slab, where that load is not adequately distributed by the slab to the supporting columns beneath. If the transfer slab and associated features are not adequately designed or constructed, there is a risk that columns at lower levels may effectively ‘punch’ through the slab. While there are not thought to have been any structural failures in the UK, this mechanism of failure is of particular significance as it may occur with limited or no advance warning. Therefore, relatively small inaccuracies in structural modelling, load assumptions or construction detailing can have disproportionate consequences on structural performance.
Regulatory and professional concern
In November 2024, the Institution of Structural Engineers (IStructE) published new guidance on the design of transfer slabs. While the guidance provides a comprehensive framework for new construction, it also highlighted an uncertainty as to whether some historic design approaches adequately addressed the risk of punching shear, particularly in relation to:
- The complex interaction between offset columns above and below a transfer slab
- The susceptibility of thick reinforced slabs to long term shrinkage
- The influence of temporary works and construction sequencing on structural behaviour
The guidance does not conclude that existing buildings incorporating transfer slabs are automatically unsafe and expressly states that non-compliance with the new recommendations does not, of itself, imply structural inadequacy or statutory non-compliance.
These professional concerns were subsequently reinforced through commentary issued by CROSS-UK in December 2024, and subsequent correspondence from the Government and the BSR in December 2025, which sought to clarify how risks associated with transfer slabs can be identified and proportionately managed in existing buildings.
Current position
Given the recent guidance does not suggest that all transfer slabs are inherently unsafe, the current regulatory response is intended to be risk-based rather than a blanket safety alert.
Pending the publication of further guidance, the BSR has advised building owners to remain informed, establish whether their buildings incorporate transfer slabs and to seek appropriate professional advice where there are visible signs of distress or specific concerns regarding design or condition. This approach reflects the BSR’s emphasis on early identification, informed assessment and proportionate risk management through the engagement of structural engineers to assess relevant buildings for potential issues arising from transfer slabs.
Remediation challenges and practical implications
Where concerns arise in relation to the performance of a transfer slab, remedial works can be complex and disruptive. Inspection and remediation may require access to either the upper surface or the underside of the transfer slab. In practice, the feasibility of such access may depend on what has been constructed above or below the slab.
Notably, in residential buildings, these constraints can present significant practical challenges. Intrusive investigations, temporary propping or strengthening works may not be feasible with occupants in situ and thus may necessitate a decant of the property.
Concerns regarding transfer slabs gave rise to several notable cases during 2025 and reflect the increasingly active role of tribunals under the post-Grenfell building safety framework:
- Wooton Court, London
The First-tier Tribunal granted a remediation order in relation to a 12-storey residential building at Wooton Court. The tribunal considered expert evidence identifying cracking around key support columns and the first-floor slab, which was indicative of a potential punching shear issue, concluding that the severity of the risk justified emergency evacuation.
- Stratford Halo Village, London
Residents of the Stratford Halo Village development were evacuated at short notice, following structural investigations that raised immediate concerns regarding building stability and transfer slab construction. Residents have since commenced legal proceedings against the building owner, alleging breaches of the Defective Premises Act 1972 (as amended).
Limitation, the Defective Premises Act and the Building Safety Act
One reason the construction sector has largely avoided widespread liability for the recently reported widespread issues relating to the use of Reinforced Autoclaved Aerated Concrete (RAAC) is the operation of limitation (see article here). RAAC was predominantly used from the 1950s to mid-1980s, with the result that many affected buildings fell outside applicable contractual and statutory limitation periods.
Issues relating to transfer slabs may present a materially different limitation profile. As they have been widely used in UK construction more recently, many buildings incorporating potentially defective transfer slabs are likely to have completed less than 30 years before 28 June 2022 (when the Building Safety Act (BSA) 2022 came into force). Complete limitation defences are unlikely to be available in relation to any claims pursued against those responsible for the design and/or construction of transfer slabs found to be defective, where the Defective Premises Act 1972 (as amended) applies.
Commentary
While it remains unclear how many buildings may feature issues relating to transfer slabs, given the increased focus on structural assessment through safety case reporting under the BSA and the recent First Tier Tribunal decisions, we are likely to see a greater number of structural investigations being undertaken on properties which feature transfer slabs.
As with fire safety investigations related to cladding, these investigations sometimes identify unrelated issues.
It is reasonable to anticipate that some claims will arise, particularly where defects or inadequacies are identified or where warning signs may not have been appropriately addressed.
Potential exposure may arise, among others, for:
- Design and build contractors and structural engineers involved in historic design and construction of buildings incorporating transfer slabs.
- Surveyors involved in pre-acquisition due diligence, where visible signs of structural distress may have been present but were not adequately identified.
- Managing agents who failed to commission appropriate condition surveys or investigations during a project’s lifecycle.
For the present, the BSR and professional bodies continue to emphasise the importance of balance rather than alarm. Transfer slabs have performed successfully in many buildings for decades, and the issuance of new guidance does not imply systemic failure. However, the recent statements by the BSR and others make clear that transfer slabs may, in certain circumstances, warrant renewed scrutiny as part of the UK’s evolving approach to building safety.
We advise clients across the construction and insurance sectors on building safety and related disputes, including matters arising under the Building Safety Act 2022 and Defective Premises Act 1972. If you would like to discuss how emerging issues relating to transfer slabs may affect your projects, please contact Ian Masser, Nathan Modell or Nick Kenny.
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