A Collaborative Effort
Completed in 2024, One Leadenhall now stands 35-storeys tall in London’s historic heartland, delivering 420,000 square feet of premium office space. Developed by Brookfield Properties and designed in collaboration with Make Architects and Adamson Associates, the project has been a major undertaking for us at Robert Bird Group, as we have acted as structural and geotechnical engineers since 2016.
Our involvement builds on a strong, longstanding relationship with Brookfield across multiple international projects, including 100 Bishopsgate in London, ICD Brookfield Place in Dubai, and Wynyard Place in Sydney. That continuity of collaboration was central to delivering a successful outcome.
We sat down with project directors Matt Quilty, Paola Caporaletti and Russell Whitehead to gain their expert insights on the engineering innovations that made One Leadenhall possible, as they reflected on almost a decade of work.
A Complex Urban Site
The location of One Leadenhall, right at the centre of the Square Mile, presented a considerable challenge. Occupying a small footprint of just 55 metres by 55 metres, the central-London site is surrounded by busy roads and Transport for London assets. Critically, its southern and eastern boundaries sit directly against the historic Leadenhall Market, a beautifully ornate, glass-roofed structure built in 1881.
The proximity to this delicate Grade II* listed Victorian structure meant that minimising movements during demolition, excavation and construction was a key technical challenge for our engineers. Additionally, the constrained site left very little room for staging, deliveries, or temporary works, making the structural solutions and construction logistics interdependent from the outset.
“The site generated all the structural challenges. It’s such a tight site, right smack in the centre of London.” – Matt Quilty
Reusing Existing Infrastructure
A defining feature of our team’s approach was the decision to reuse elements of the site’s existing building, a 1980s office block. While the superstructure of the old building had to be demolished, its basement walls remained in excellent condition and were identified as suitable for reuse. Retaining these walls removed the need for entirely new retaining structures such as secant piles, saving time, reducing cost, and avoiding unnecessary material use.
We made this possible by reverse-engineering the original basement slab. By cutting and reconfiguring it into a doughnut shape, the slab could continue to prop the existing walls during excavation. This inventive method allowed the excavation of an additional basement storey through the centre of the footprint, enabling the installation of a new raft and pile foundation system and the construction of the new reinforced concrete core. The approach kept the ground stable, minimised settlement, and ensured the adjacent market remained unaffected.
Safeguarding a Historic Neighbour
With Leadenhall Market immediately next door, protecting its sensitive wrought-iron structure was one of the project’s most pressing requirements. From the earliest design stages, our geotechnical and structural teams worked hand in hand to minimise movement and safeguard the market against any adverse effects from the works at One Leadenhall.
This required close coordination with the party wall engineer, strict adherence to movement criteria, and the strategic sequencing of works to reduce risks at every stage. Advanced monitoring strategies were also implemented to track settlement and ensure the market remained stable throughout.
“When we deal with heritage structures, typically, these structures are even more sensitive, and therefore, interface management is crucial for the success of the project.” – Paola Caporaletti
A Sustainable Foundation Solution
Beneath the tower, one of the most significant innovations was the adoption of a pile-assisted raft foundation. Instead of relying solely on very deep piles, the design combined a robust raft slab bearing directly on London Clay with 100 piles, each 30 metres deep. This hybrid system balanced the load between raft and piles, controlling settlement while reducing material demand.
By making full use of the ground’s bearing capacity and limiting the number of piles required, the solution not only satisfied the tight movement tolerances but also delivered considerable sustainability benefits. Concrete volumes were reduced by around 20%, resulting in an equivalent saving in embodied carbon. These efficiencies underline the value of integrating geotechnical expertise into the structural design process from the start.
Complex Structural Design
Above ground, One Leadenhall is defined by a four-storey podium with colonnades at street level, above which rises the set-back 35-storey tower. The tower is split into three slices, with façades stepping in and out to break down the overwhelming mass of the building and complement its historic surroundings.
Delivering this form required sophisticated transfer structures. We employed raking columns to redistribute loads and enable office floors to extend beyond the basement footprint. These angled columns lean outwards at the base and then transfer loads back into the core and basement, ensuring the tower achieves maximum lettable area while staying within the physical limits of the retained basement walls.
Early Certainty in Construction
The project demonstrates the value of integrating construction methodology into design from the outset. Early collaboration with the contractor Multiplex enabled the sequencing of works and crane placement to be planned in detail before construction began.
One key innovation was the decision to locate the main crane outside the building footprint, allowing construction to proceed without interruption across the site and avoiding the need to dismantle a crane before services could be installed in the core. This early certainty allowed the programme to be streamlined, deliveries to be coordinated effectively, and congestion to be minimised on a constrained city-centre site.
“What this project really embodies is the benefit of upfront certainty around construction methodology and logistics.” – Russell Whitehead
Innovations Built on Experience
While many of the engineering strategies adopted at One Leadenhall were novel in their application to this specific site, they also represent a continuation of approaches we have developed on other major projects. Innovations such as the piled raft foundation, climbing crane systems, and advanced geotechnical modelling are part of a philosophy of continuous improvement that we apply to projects globally.
This progressive approach to innovation means each project contributes lessons and refinements that are then carried forward, delivering more efficient and sustainable outcomes with each application. One Leadenhall is a prime example of this process, where previous experience underpinned the confidence to apply inventive solutions on a highly sensitive site.
“The innovations that we found on this project were all about stepped improvements of innovations that we’ve done elsewhere.” – Matt Quilty
A Successful Outcome
One Leadenhall is the culmination of almost a decade of work at Robert Bird Group, spanning concept design, demolition, excavation, foundation construction, and superstructure delivery. For the team, one of the most significant achievements is that the adjacent Leadenhall Market remained unscathed.
The project’s successful completion is an outstanding technical accomplishment made possible by exemplary collaboration across various disciplines and stakeholders. Now a striking addition to the city skyline that respects its historic surroundings and provides a dynamic workplace for thousands of Londoners, One Leadenhall demonstrates how engineering ingenuity can unlock ambitious developments in even the most constrained urban environments.
“It’s been a really good eight or nine years, and it’s rewarding to finally see the building complete, looking fantastic. And what a great bunch of people – I’m looking forward to celebrating on the public roof terrace on level four of One Leadenhall in the near future.” – Russell Whitehead