Transfer slabs (being thicker than normal) can be prone to internal stresses due to curing heat and shrinkage, which can also cause tension cracking, particularly where floors and core walls abut. Visible deflection beneath columns may indicate a problem however, it can be difficult to identify such movement without very detailed measurement, particularly in occupied buildings, where this is often concealed by suspended ceiling finishes.
Are there any reports of failures in transfer slabs?
There are currently no confirmed collapses that have been attributed to transfer slabs, but several high-profile evacuations have occurred. At Wotton Court, cracking around load-bearing columns suggested punching shear, leading to its emergency evacuation and mandated remediation under the Building Safety Act 2022. Whereas, at Stratford Halo in London, multiple blocks were evacuated amid structural concerns, with punching shear suspected as a possible factor.
What guidance is now available?
IStructE published its “Design of Transfer Slabs” guidance in November 2024 (ii), providing recommendations for both new designs and the assessment of existing structures.
RICS followed with a Practice Alert in January 2026, advising 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 identify potential transfer slabs, but detailed analysis must be undertaken by suitably qualified structural engineers.
Should building owners be concerned?
Yes and no. The presence of a transfer slab does not mean a building is unsafe or requires evacuation. However, it does warrant awareness and, where appropriate, further investigation.
A sensible first step is to establish whether a transfer slab exists, typically through a review of drawings and, where necessary, site inspection. And where concerns arise, structural engineering input will be required. However, pay very careful attention to visible areas to see if there is any evidence of cracking, deflection in floors, lack of verticality in columns or other defects that warrant further investigation.
How does the matter affect surveyors?
Surveyors are now expected to be aware of transfer slabs and their potential risks. Identifying their presence, or the possibility of it, and recommending further investigation will increasingly form part of standard practice.
