Transfer Slabs – Recent Concerns and what you need to know

This brief information paper is intended to explain the background to the problem, the role of transfer slabs and the actions that might be required.

What is a transfer slab and where might one be found?

A transfer slab is simply a thick reinforced concrete floor slab where a column sits on top of a slab but does not have a column immediately below. In other words, it bridges between supporting columns and provides support to columns from the upper parts of a building. Transfer slabs are common in residential and mixed-use commercial buildings, purpose-built student developments and many high-rise structures. Typical uses would include where the column spacing on the ground floor of a building (possibly commercial space) is greater than the spacing on the first floor and above, or where successive floor plates step back from one another to form terraces.

What is the concern?

Columns transfer vertical loads to the foundations or other loadbearing elements of a building. The actual load paths can be complex and, in many cases, depend upon the methods used in the design and execution of temporary works when the building is constructed. Furthermore, concrete buildings tend to shrink over time, and this can lead to potentially significant changes in the way that the loads are transferred. Because a transfer slab is taking point loads it must be designed to accommodate the risk of punching shear – the potential for the column to “punch” through the slab in much the same way that a pencil could be pushed through the lid of a cardboard box. Doubts have been expressed over the design methodology applied to the design of slabs in this scenario.

What are the symptoms of punching shear?

One of the difficulties with punching shear is that it is what is termed a brittle failure mode. This means that failures can be sudden, with little or no plastic (permanent) deformation. An early precursor can be the discovery of cracking in the structure, but this cannot be expected to occur in all cases or evidence might be misleading. Indeed, transfer slabs (being thicker than normal) can suffer from significant internal stresses as a result of heat created during curing and longer-term shrinkage – this can also result in the onset of tension cracking particularly where floors and core walls abut. Clearly, evidence of deflection in a flat slab beneath a column might trigger concern, but in an occupied building, particularly with suspended ceiling finishes, it might be very difficult to identify such movement without very detailed measurement.

Are transfer slabs designed using established principles?

No, there are various design and modelling methods but until the end of last year, no universally accepted methodology. Whereas at one time British Standards were usually quite prescriptive, their replacements, in 2005, by the Structural Eurocodes (BS EN1990-1999) are more performance based. Whilst BS 8110 has been withdrawn, compliance with Building Regulations is not dependent upon a specific code as long as the functional requirements are met (iii). Thus, there is scope for various design methodologies including software-based techniques such as finite element analysis; this is all well and good, but the uncertainty lies in the lack of consistency, the complexity of the different forces at play and the risk that a “one size fits all” approach to design can fail to provide adequate capacity.

So, what has been done to address the problem? 

The Institution of Structural Engineers has published guidance on this issue, see Design of Transfer Slabs in November 2024 (iv).  The guidance can be downloaded freely from the Institution’s website. Although primarily intended for engineers to establish standard methodologies in design, the guide also provides advice in the verification of existing structures; something that ultimately will require engineering input.

What has RICS recommended?

In its Practice Alert of 14th January 2026 (v), RICS draws mainly upon the Building Safety Regulators advice of 19th December: “The government is currently recommending that where there are visible signs of distress or specific concerns regarding a building’s condition or design, building owners should seek immediate professional advice. RICS members who are chartered building surveyors may be instructed to carry out condition surveys of such tall buildings to identify buildings with transfer slabs. If a building is identified, then a suitable expert structural engineer will be required to carry out more in-depth analysis. RICS recommends that IStructE are contacted for suitable competent engineers.”

Is there reason to be concerned?

Yes and no. Clearly the risks are such that a warning should be issued, but the mere existence of a transfer slab does not mean that failure is inevitable or that immediate steps need be taken to evacuate the building or to provide additional precautions against collapse. The BSR is currently working with the Building Advisory Committee in co-operation with MHCLG and so further guidance is likely to be issued in due course. Unless there is unmistakable evidence of a problem the BSR’s advice could be seen as somewhat of a “hurry up and wait” approach.

However, a prudent first step would be to review any potential cases to see if a transfer slab is likely to exist and thus start to narrow the issue down to more manageable proportions. Such an exercise ought to be within the remit of suitably experienced Chartered Building Surveyors in the first instance but detailed analysis is something that will demand structural engineering advice. A desktop study of construction drawings ought to indicate whether there is potential for a transfer slab, but this will probably need to be followed up by site inspection. Examination of the structural philosophy (if it is within the health and safety file) may also show whether transfer slabs have been employed.

On current projects, the engineering aspects of the design can be reviewed against the latest IStuctE guidance but for existing buildings, the trail may be less certain with the potential need for non-intrusive tests or exploratory work to confirm the design and reinforcement details in relevant cases.

How does the matter affect surveyors?

Given the RICS Practice Alert, regulated firms need to have regard to the nature of the concerns and would be expected to have regard to the guidance available at the time of any survey. This would probably include the identification of a transfer slab (as opposed to a slab designed with downstand beams) and, usually, a recommendation for further enquiry. As RICS warns “RICS members who believe that a building may have a transfer slab, should advise the building owner to instruct a suitably qualified and competent CEng member of the Institution of Structural Engineers or Institution of Civil Engineers, satisfying themselves that such professionals have expertise in this area.”

In addition to the above, and specifically in relation to High Rise Buildings, it is possible that Building Safety Case Reports may need to be re-visited and amended. (vi) 

A detailed analysis of a transfer slab is something that is outside the remit of the average Chartered Building Surveyor, but recognition of the form of structure is not and there will now be a reasonable expectation that a surveyor will have flagged the existence or possible existence of this form of construction and made appropriate recommendations for further advice.

Conclusion

In summary, while the recent alerts from the Building Safety Regulator, IStructE and RICS highlight legitimate concerns around the design and performance of transfer slabs, it does not necessarily follow that the construction is defective.  The alerts serve as a prompt for building owners, surveyors, and engineers to review existing structures and to see that appropriate professional expertise is engaged where uncertainties arise.

By adopting a proportionate, evidence‑based approach—beginning with the identification of potential transfer slabs and escalating to specialist engineering appraisal only where justified—the industry can manage risk sensibly while awaiting further clarity from the regulator. Understanding, careful documentation and early engagement with competent structural engineers will be key to ensuring building safety, regulatory compliance, and continued confidence in the built environment.

Trevor Rushton FRICS FCABE ACIArb, Group Chairman. Watts