Transfer slabs are quickly becoming one of the most important emerging building-safety and professional indemnity issues for the construction sector.
They are not new. In fact, they have been used widely in UK residential and mixed-use developments, particularly from the early 2000s onwards. What has changed is the level of scrutiny being applied to their design, construction and assessment, and the consequences for those involved in historic projects.
The concern is not that every building containing a transfer slab is unsafe. It is that some historic design methods may not have properly assessed the way concentrated column loads pass through the slab. If a weakness exists, the resulting claims could resemble the cladding disputes that have already affected contractors, developers, consultants and insurers across Essex, Kent, London and the wider UK.
What is a transfer slab?
A transfer slab is a heavily reinforced concrete structural element that redistributes building loads where the columns above do not line up with the columns or walls below.
This arrangement is common where a building changes use or layout between floors. For example, a development may have a wide column grid for retail units, a car park or an open podium at lower levels, with a tighter column grid supporting apartments above.
The transfer slab effectively carries the loads from the upper columns and transfers them sideways or across the slab to the supporting structure below. This creates valuable design flexibility, but it also creates a more complicated structural load path.
Transfer slabs are often found in:
- Mixed-use residential developments
- High-rise and medium-rise apartment buildings
- Buildings with retail or commercial space below residential floors
- Podium developments over underground car parks
- Hotels and buildings with changing column layouts
- Some buildings with setbacks, roof gardens or stepped façades
The Institution of Structural Engineers has noted that transfer slabs became increasingly common during the last two decades, helped by design-and-build procurement, flat formwork and the availability of advanced finite element modelling software.
Why is punching shear the main concern?
The central concern is punching shear.
This is a localised failure mechanism where a concentrated load from a column causes a section of concrete to punch through the slab. It is different from a straightforward bending failure and can be brittle, sudden and difficult to detect in advance.
The risk is especially important where columns above and below are closely spaced or significantly misaligned. Standard punching shear calculations may not always reflect the concentrated and uneven flow of forces through a transfer slab.
The potential consequences are serious. A local failure may affect the surrounding structure and, in a severe case, contribute to partial or progressive collapse. The Building Safety Regulator has confirmed that it is not aware of a UK building collapse caused by transfer slab failure, but it has warned that the potential risk needs to be identified and managed proportionately.
That distinction matters. The presence of a transfer slab is not, by itself, evidence of a defect. The practical question is whether the slab was properly designed, detailed, constructed, maintained and subsequently assessed.
The regulatory and technical warning signs
The Building Safety Regulator issued a warning to building owners and principal accountable persons in December 2025. It highlighted a potential structural safety issue affecting reinforced concrete buildings constructed with transfer slabs, with particular concern around punching shear.
The warning encouraged owners to establish whether their buildings contain transfer slabs and to seek professional advice where there are visible signs of distress or specific concerns about the building’s condition or design. It also stressed that the presence of a transfer slab does not automatically mean residents should be evacuated.
RICS subsequently issued advice and a Practice Alert, followed by further communications in March 2026. Its guidance is aimed at helping surveyors and other professionals recognise when a transfer slab may be present and understand when a specialist structural engineer should be appointed.
In July 2026, IStructE published its Q&A and guidance, Design and Assessment of Reinforced Concrete Transfer Slabs. This is an important development because the earlier November 2024 guidance focused mainly on new-build design. The July update recognises the urgent need to identify and assess slabs that are already in service.
The current position is interim. IStructE is developing dedicated assessment guidance for existing transfer slabs, expected in 2027. In the meantime, the existing design guidance can be used carefully as a benchmark for assessments, with appropriate consideration of the age, construction quality, available records and limitations of applying modern criteria to older buildings.
Wotton Court shows how quickly the issue can become a legal problem
The issue has already reached the First-tier Tribunal.
In December 2025, the Tribunal made a remediation order concerning Block P, Wotton Court, a 12-storey residential building at the Virginia Quay development in Poplar, London. Residents had been required to vacate part of the building after cracking was identified around supporting pillars and the first-floor slab.
Engineering evidence indicated that punching shear failure was highly likely, although further investigation was needed to establish the precise cause and extent of the defects. The Tribunal ordered the relevant landlord to carry out a full building-wide structural investigation and remedy the defects, including any underlying causes.
The decision is significant because the order was not limited to a temporary fix. It required the relevant defects to be fully remedied, while leaving the precise engineering solution to be determined through competent investigation and design.
For building owners and managers, this demonstrates that structural defects can fall within the Building Safety Act 2022 remediation regime, not just cladding and fire-safety issues. For contractors and consultants, it shows how historic work can be revisited many years after completion.
The Building Safety Act increases the potential reach of claims
The Building Safety Act creates several routes through which remediation costs and liabilities may be pursued.
Remediation orders can require a relevant landlord to carry out works. Remediation contribution orders can then potentially require developers and associated companies to contribute to the cost. Building Liability Orders may also extend liabilities across a corporate group in appropriate circumstances.
The courts and tribunals have shown a robust approach. In Edgewater v Grey GR, the Upper Tribunal confirmed that remediation contribution orders can impose joint and several liability and that the “just and equitable” test does not necessarily require direct participation in the development or financial gain from it.
In Secretary of State v EDR Builders, the Tribunal also rejected the idea that a remediation award must automatically be reduced simply because a cheaper scheme could have been used. If the works fell within the band of reasonable responses based on the information available at the time, the existence of a cheaper alternative was not, by itself, enough to reduce the award.
These decisions sit alongside the wider lessons from cases such as Mulalley v Sto and our article on Building Liability Orders and the whole company group.
The message for construction businesses is straightforward: a dormant project company or a complicated corporate structure may not prevent historic liabilities from being pursued.
What does this mean for professional indemnity insurance?
Transfer slab claims may involve several categories of insured professional activity, including:
- Structural design and engineering
- Architectural coordination
- Specification and detailing
- Design checking and verification
- Construction and reinforcement placement
- Site inspection and certification
- Building surveying and later assessment
- Warranty and technical review
Potential losses may include investigation costs, temporary propping, access arrangements, remedial design, construction works, alternative accommodation, diminution in value and claims arising from structural failure.
Construction professional indemnity insurers are likely to scrutinise the quality of risk management and quality assurance on historic projects. They may also face complex disputes about who was responsible for the design, whether the design was properly checked, what information was available, whether the construction matched the drawings and when the insured first became aware of a potential issue.
The recent decision in Durkan v Wallace is also a reminder that building-safety disputes can become fact-heavy and protracted. Delay, regulatory approval, contractual responsibility and the parties’ conduct may all need to be examined before liability or recovery prospects are clear.
This is why notification obligations matter. If a contractor, engineer, surveyor or consultant becomes aware of a circumstance that may give rise to a claim, it should review the policy wording and seek advice promptly. Waiting until a formal claim or remediation demand arrives can create avoidable problems.
Our guide to professional indemnity cover for contractors explains why contractual and historic design exposure should not be overlooked.
Practical steps for contractors and professionals
If your business designed, specified, built, inspected or certified residential or mixed-use buildings with transfer slabs from around 2000 onwards, I think a proportionate historic review is sensible.
Start by identifying projects where transfer slabs may have been used. Review project drawings, structural calculations, reinforcement details, inspection records, completion information and any later reports. Pay particular attention to higher-risk buildings and developments where the column layout changes substantially between floors.
You should also:
- Establish what your business’s precise role was on each project.
- Check whether design responsibility was retained, transferred or shared.
- Review quality assurance, reinforcement inspection and concrete-pour records.
- Preserve project records and maintain a clear audit trail.
- Identify circumstances that may need to be notified to PI insurers.
- Ensure all new transfer slab work follows current IStructE guidance.
- Obtain specialist structural advice rather than relying on a general inspection.
- Record assumptions and limitations where historic information is incomplete.
For new work, the IStructE guidance should be treated as an important part of the design and verification process. For existing buildings, the assessment should be carried out by a suitably experienced structural engineer and should consider actual geometry, reinforcement, materials, construction quality, loads, cracking, deflection and the wider consequences of failure.
What should building owners and managers do?
Owners and managers should first establish whether a transfer slab exists. This may require a review of original drawings, building information models, structural calculations and as-built records.
Signs such as cracking, deflection, sloping floors, distorted finishes or misaligned doors and windows should not be dismissed where they occur near a suspected transfer slab. They do not prove a structural defect, but they may justify further investigation.
For a higher-risk building, the presence or absence of transfer slabs should be addressed in the safety case and risk register. Existing safety case reports may need updating as better information becomes available.
The appropriate response will depend on the building. It may be no further action, monitoring, targeted investigation, detailed analysis, strengthening or urgent temporary measures. A blanket response is not appropriate, but neither is ignoring the issue.
Insurance support for contractors in Essex, Kent and London
Transfer slabs are a structural issue, but the financial consequences will often be managed through construction insurance, professional indemnity policies and wider business risk controls.
Whether you are looking for Construction Contractor Insurance, General Contractor Liability Insurance or a broader review of your Business Insurance Essex or Business Insurance London arrangements, the important point is to discuss the actual work your business undertakes and the historic exposure it carries.
At Moyak Insurance Services, we take an individual approach because no two contractors have the same contracts, responsibilities or claims history. The right cover depends on whether you design, build, certify, inspect or manage work, and how your policy responds to historic projects and professional services.
Transfer slabs may prove to be the next major legacy construction risk to move from technical guidance into widespread remediation disputes. Contractors, developers, structural engineers and property owners should not wait for the first formal claim before reviewing their records, responsibilities and insurance position.
This article is for general information only and does not constitute structural, legal or insurance advice. Building owners and construction professionals should obtain advice from suitably qualified structural engineers, solicitors and insurance advisers based on their individual circumstances.
Frequently asked questions
What is a transfer slab?
A transfer slab is a heavily reinforced concrete slab that carries and redistributes loads where columns above do not align with the columns or walls supporting the structure below.
Are all buildings with transfer slabs unsafe?
No. The presence of a transfer slab does not, by itself, mean that a building is unsafe or needs to be evacuated. The design, construction, condition, loading, detailing and consequences of failure must be assessed on a building-specific basis.
What is punching shear?
Punching shear is a localised failure mechanism where a concentrated column load causes a section of concrete to punch through a slab. It can be brittle and sudden, which is why it is a key concern in transfer slab assessments.
Could transfer slab defects lead to an insurance claim?
Potentially. Deficiencies in design, specification, construction, inspection or later assessment may lead to professional negligence, construction liability or remediation claims. Policy response will depend on the wording, the insured’s role, the date of the work and notification requirements.
What should a contractor do if it worked on a building with transfer slabs?
The contractor should identify the project, establish its precise contractual and professional role, preserve relevant records and review whether notification to its professional indemnity insurer is required. It should also obtain specialist advice before making technical or legal conclusions.