Defective transfer slabs in buildings: a new wave of claims?

Both the Building Safety Regulator (BSR) and RICS have recently issued warnings regarding a potential structural defect affecting reinforced concrete buildings with transfer slabs.  

This article reflects on the issues that the historic design of transfer slabs presents for professionals and their insurers, the possible defences available to them, and the likely extent of claims on the horizon. 

What is a transfer slab?

A transfer slab is a reinforced concrete floor which transfers loads from upper level columns to a different column arrangement below. Transfer slabs have been a common design feature in the UK for the last 25 years, particularly in high-rise and mixed-use developments. This is because they allow designers to create open spaces, such as car parks, retail spaces beneath commercial offices or residential apartments, or to facilitate a step back in the façade to allow for a roof garden space.

What is the risk?

In November 2024, the Institution of Structural Engineers alongside the Concrete Centre and AECOM published crucial guidance for designing reinforced concrete transfer slabs. The guidance addressed gaps in knowledge surrounding the design of transfer slabs, and suggested that some older design methods might not meet modern safety standards.

The primary risk associated with transfer slabs relates to ‘punching shear’, which is where a column ‘punches’ the slab, which can lead to localised or progressive collapse. The failure of a transfer slab can potentially lead to partial collapse of the building. The ramifications for building owners and the parties who were involved in the design and construction of these slabs could therefore be significant.

The BSR is working with industry experts and the government to better understand the extent of the risk, and how the risk can be identified and managed proportionately in existing buildings.

The presence of a transfer slab alone does not mean a building is unsafe, and the BSR has stated this should not immediately trigger building evacuation. We also stress that the BSR has not, to date, noted any building collapses due to this issue.

However, the BSR is calling for urgent structural engineering reviews, particularly in mixed-use, high-rise, or 18m+ buildings; or in lower risks buildings where there are already signs of structural distress.

Claims

Where issues are identified, we can expect to see claims against the Design & Build contractor and/or structural engineers arising out of buildings designed and constructed over the last 25 years. 

We may also see claims against surveyors involved in the pre-purchase due diligence of buildings (particularly if there were visible signs of distress like cracking) and management companies who failed to undertake condition surveys during a buildings’ lifecycle.

 As buildings come under greater scrutiny (with widespread structural reviews being carried out) it is likely that other issues/defects will be discovered giving rise to claims, as we have seen with the post-Grenfell cladding claims.

Defences

Limitation

Subject to when the building was constructed and completed, and when the defect was identified, there may be limitation defences available to the contractor and/or design consultants involved.

However, with regards to residential buildings, claims under the Defective Premises Act 1972 (DPA) now have a 30 year retrospective limit (before June 2022) and a 15 year prospective limit (after June 2022).  This means that if there is a defective transfer slab within a residential building, it is unlikley to face statutory limitation hurdles given that this method of construction has only been commonplace in UK construction for the last 25 years.

The slab was not defective/non-compliant at the time of construction/completion

Another likely defence argument will be that the transfer slab was compliant with the relevant standards at the time of construction. The new guidance only suggests that the historic methods may not meet current standards.

Indeed, the new guidance expressly acknowledges that “there will be transfer slabs that were designed before the publication of this guidance which may not comply with all the recommendations in this guide. Non-compliance with this guidance does not necessarily lead to the conclusion that the design of an existing slab is structurally inadequate or statutorily non-compliant.”

Alternatively, it may be arguable that the building in question was fit for habitation (in accordance with the DPA) when it was completed, but the slab has deteriorated over time and/or has come to the end of its design life.

Reasonable skill and care

Even if it can be demonstrated that the design was non-compliant with the relevant standards at the time, it may still be arguable that the designer acted with reasonable skill and care (or in a ‘professional manner’ in the case of a DPA claim) on the basis that e.g. the design was common industry practice, the design followed common modelling methods, and until November 2024, the risks were not known about and there was no universally accepted methodology. Of course, each case will need to be determined on its own facts.

Comment

It is currently unclear how many buildings might be affected by this issue. The current focus for building owners is on investigating the issues (with input from structural engineers and/or building  surveyors) to establish the extent of the risk and the gravity of any temporary and permanent remedial works required. That will be more difficult to establish for older buildings where the engineering aspects of the design may no longer be available and intrusive investigations may be required to confirm the design.

Indeed, the First Tier Tribunal recently (December 2025) ordered a building owner to undertake a full building-wide structural engineering survey to identify the cause of defects to a transfer slab, which was unclear from the expert evidence.

Only time will tell whether and to what extent claims arise from those ongoing and future structural engineering reviews of buildings. However,  based on what we have seen to date, and given the likely defences available, we do not anticipate a flood of claims in the manner of the post-Grenfell fire safety litigation. That being said, claims will inevitably arise and the construction industry and insurance sector need to be alive to the issues and be ready to respond.