London's skyline is usually described through architecture. The Shard is Renzo Piano. The Leadenhall Building is instantly recognised by its tapered profile. 22 Bishopsgate dominates the City cluster. Canary Wharf is defined by towers that have become landmarks in their own right. But behind almost every famous silhouette is another name that receives far less public attention: the structural engineer who worked out how the building could actually stand up.
London's tallest buildings are not simply vertical stacks of floors. They are enormous load-transfer machines designed around wind, gravity, movement, foundations, railway tunnels, neighbouring structures, archaeology, construction sequence and the geology beneath the capital. Sometimes the solution is a reinforced-concrete core. Sometimes it is an external steel megaframe. Sometimes new piles have to be threaded through the foundations of a demolished building.
In one of London's most remarkable examples, an entire new skyscraper was designed around foundations left behind by a previous tower that was never completed. And when the major towers are mapped by structural engineer rather than architect, a striking pattern emerges.
London's skyline reflects decades of increasingly complex structural engineering, with tall buildings rising alongside the capital's historic urban fabric. Photo: London Construction Magazine.
A surprisingly small group of engineering firms appears repeatedly behind London's most ambitious buildings. While London's tallest buildings are usually remembered by their architects and silhouettes, London Construction Magazine analysis shows that a concentrated group of structural engineering firms solving extreme foundation, stability, transfer and reuse problems leads to a much more revealing story behind the skyline.
By the Numbers: The Engineers Behind London's Skyline
| Structural Engineering Firm | Representative London Towers Identified | Engineering Signature | Future / Pipeline Signal |
| WSP | The Shard, 22 Bishopsgate, Newfoundland, Landmark Pinnacle, Principal Tower, South Quay Plaza | Supertalls, deep foundations, structural reuse, constrained sites, high-rise concrete and steel | One London / 1 Undershaft |
| Arup | Leadenhall Building, 52 Lime Street, 30 St Mary Axe, 8 Canada Square, 8 Bishopsgate | Steel megaframes, material optimisation, complex geometry and integrated engineering | Continued role across complex commercial and low-carbon engineering |
| AKT II | One Park Drive, One Nine Elms, One Crown Place | Complex geometry, residential towers, transfer structures and structural reuse | 99 Bishopsgate and other late-decade schemes identified in the research |
| Robert Bird Group | 100 Bishopsgate and complex City construction-engineering work | Complex substructures, construction engineering, temporary works and constrained City sites | 85 Gracechurch Street and further major City pipeline involvement |
| Halcrow Yolles / Yolles heritage | 20 Fenchurch Street; historic Canary Wharf engineering lineage | Complex steel high-rise structures and geometry-led tower engineering | Historic influence remains visible in London's earlier tower generation |
| MS Yolles / Waterman and associated teams | One Canada Square and early Canary Wharf generation | Large steel commercial towers and docklands foundation engineering | Important historical benchmark for today's engineering market |
Methodology note: This is not a market-share table or a claim that every London tall building has been captured. Firms are shown where repeated project-level attribution could be established across the research reviewed to 14 August 2026. Concept design, permanent structural engineering, contractor design, temporary works and checking roles have been separated where the available evidence allowed.
WSP Appears Most Often Behind London's Tallest Buildings
Across the completed and future towers reviewed, WSP is the structural engineering firm that appears most frequently. The list is substantial: The Shard, 22 Bishopsgate, Newfoundland, Landmark Pinnacle, Principal Tower, South Quay Plaza and the future One London / 1 Undershaft all appear in the researched portfolio. What makes that position interesting is not simply the number of buildings. The projects require completely different structural responses.
The Shard uses a hybrid structural strategy that transitions through steel and concrete as the tower rises. 22 Bishopsgate had to inherit and adapt foundations from the abandoned Pinnacle scheme. Newfoundland uses a structural arrangement responding directly to underground railway infrastructure. Principal Tower required foundation design around existing rail tunnels. That breadth is more revealing than a simple company ranking. Tall-building engineering is not one specialism. It combines structural dynamics, geotechnics, construction sequencing, material optimisation, temporary stability, façade movement and increasingly the question of how much existing structure can be retained.
22 Bishopsgate: The Skyscraper Built on Another Skyscraper's Foundations
If one building demonstrates why structural engineering deserves more attention, it is 22 Bishopsgate. Before the 278m tower existed, the site was intended for The Pinnacle. That earlier project stalled after substantial substructure work had already been completed, leaving behind a three-storey basement, part of a concrete core and deep piles. Starting again from a clean site would have been structurally simpler.
Instead, WSP designed the replacement tower around what was already underground. The project incorporated 100% of the previous foundation system and around half of the existing basement structure. The complication was that The Pinnacle's foundations had been designed around a different tower geometry. Its deep piles followed an oval arrangement while 22 Bishopsgate required a larger and more regular structural grid. New small-diameter piles therefore had to be installed between an existing forest of foundations while the new tower's loads were redistributed through a series of transfer structures.
The researched engineering record identifies five separate steel transfer structures in the superstructure and 13 concrete or steel transfer structures at basement level, including mega-transfer girders, multi-storey A-frames and high-strength ties associated with inclined columns. Then came the construction sequence. Around 20 storeys of core could progress while foundation work was still continuing below part of it. Technical accounts reviewed for this analysis describe approximately 16,000 tonnes of reinforced core temporarily supported at basement level while the substructure beneath was completed.
In plain English: part of a skyscraper was rising while engineers were still completing the system that would ultimately support it. That is not an architectural detail. It is structural and construction engineering determining whether an enormous commercial development can be built economically at all.
The Cheesegrater Has No Conventional Concrete Stability Core
The Leadenhall Building is another building whose most interesting feature is visible to millions of people without necessarily being understood. Its steelwork is not simply architecture placed outside a conventional tower structure. The external steel megaframe is the principal stability system. Arup engineered the 225m tower without the conventional internal reinforced-concrete stability core seen in many modern skyscrapers. Instead, the perimeter megaframe and associated bracing resist the tower's lateral forces. Research reviewed for this article describes the system as the tallest steel megaframe of its type when completed. Only a small number of internal columns were required because so much structural work had been moved to the perimeter.
Why use such an unusual system? The building's famous taper responds partly to protected views towards St Paul's Cathedral. As the floorplates reduce towards the top, a conventional central stability core would consume an increasingly significant proportion of usable floor area. Moving stability to the external megaframe solved both architectural and structural problems. Construction introduced another challenge: the building would not remain geometrically fixed as additional floors and dead load were added. The solution involved an active alignment strategy in which adjustable elements at major steel nodes allowed the geometry to be corrected progressively during erection. The structure was therefore not simply designed to be straight in a computer model. Its predicted construction movement had to be designed into the erection process itself.
The Shard Changes Structure as It Gets Taller
At 309.6m, The Shard remains the reference point for extreme-height construction in London. But it is not one uniform structural frame repeated from ground to roof. The structural solution changes as the tower rises The lower commercial portion uses composite steel construction around the reinforced-concrete core. Higher levels transition towards post-tensioned concrete construction, followed by conventional reinforced concrete and finally the prefabricated steel spire. Each material is being used where its characteristics are most valuable. Steel provides speed and long-span flexibility in office areas. Concrete adds stiffness and mass higher in the tower. The lightweight steel spire completes the extreme upper structure without imposing the same mass as a solid concrete continuation.
Below ground, the challenge became even more London-specific. The previous Southwark Towers development had left under-reamed foundations that could not simply become foundations for the substantially larger Shard. Rather than attempt the enormously difficult task of extracting every old foundation, the new piles were positioned between the existing piles and their widened bases while also navigating utilities and archaeological constraints. The basement and tower were then able to progress using top-down construction, with substructure and superstructure operations overlapping rather than waiting for the entire basement to be completed first.
Technical records reviewed for this investigation describe approximately 5,500m³ of concrete being placed during the major raft pour over around 36 hours. The skyline may be visible above London Bridge, but some of the project's hardest engineering was buried long before the glass reached the sky.
London's Towers Are Standing on a Crowded Underground City
This may be the most important fact about high-rise engineering in London. Engineers are rarely designing on an empty piece of ground. Below the pavement can sit:
• London Underground tunnels;
• National Rail infrastructure;
• historic basements;
• Victorian utilities;
• sewers;
• abandoned foundations;
• archaeology;
• neighbouring pile groups;
• and assets that are expected to remain operational throughout construction.
Newfoundland at Canary Wharf is one striking example. Its structural arrangement responds to Jubilee line infrastructure beneath the site, with the tower's external structural system helping transfer loads around the underground constraint rather than simply allowing gravity loads to descend wherever the ideal column grid would otherwise place them.
Principal Tower presents another version of the same problem. Its foundation layout had to respond to historic rail infrastructure around Liverpool Street, forcing piles into positions that avoided existing tunnels. The engineering question is therefore often not: "What is the most efficient foundation for this tower?" It is: "What foundation can carry this tower through the few pieces of ground where we are actually allowed to put one?" That is why two skyscrapers only a few hundred metres apart can require radically different substructure solutions.
London Clay Is Only the Beginning
London's geology adds another layer. Much of the capital is underlain by London Clay, but tall-building foundations can extend into deeper geological formations including the Lambeth Group, Thanet Sand and, depending on location and foundation strategy, towards Chalk. That affects pile capacity, settlement, basement excavation, groundwater management and the interaction between a new building and everything already around it.
As towers become taller, small movements become increasingly important. Engineers have to consider not only total settlement but differential settlement: one part of a building moving differently from another. They also consider concrete creep, shrinkage, column shortening, frame movement during construction and the tolerances required by a façade attached to a structure that is never completely motionless.
Why London's Skyscrapers Do Not Fall Over in the Wind
Gravity is only half the problem. As a tower becomes taller and more slender, wind increasingly tries to push it sideways and make it rotate around its base. A modern skyscraper therefore needs a lateral stability system. Different London towers solve that problem differently.
22 Bishopsgate uses its reinforced-concrete core and surrounding structural frame as part of the stability strategy.
The Leadenhall Building moves that job to its external steel megaframe.
Newfoundland uses a diagrid-type external structural expression together with its internal structure.
The Shard changes material and stiffness as it rises and incorporates additional high-level structural measures as its geometry narrows.
The objective is not to create a building that never moves. That would be neither realistic nor necessary. The objective is to keep strength, deflection, acceleration and movement within the design criteria required for the structure, façade, services and people occupying the building. This is why wind-tunnel testing and specialist wind engineering appear repeatedly on major tower projects.
Arup's Skyline Is Smaller in Number but Structurally Distinctive
WSP appears most frequently in the researched tower sample, but Arup's London portfolio illustrates why frequency alone cannot measure engineering significance. The Leadenhall Building is one of the clearest examples.
Other researched Arup projects include 52 Lime Street (the Scalpel) alongside earlier London landmarks such as 30 St Mary Axe and 8 Canada Square. At 52 Lime Street, the research identified structural-steel optimisation in which beam flange and web dimensions were adjusted according to loading rather than simply standardising heavier sections throughout the building. That produced significant material savings. It is a useful indication of where high-rise engineering is moving. The next generation of structural design is not simply about making structures possible. Increasingly, engineers are being asked to make them possible with less material, less embodied carbon and greater reuse of what already exists.
AKT II Is Becoming Increasingly Visible in the Next Generation
The future pipeline begins to change the league table. AKT II appears repeatedly across complex residential and mixed-use high-rise projects including One Park Drive, One Nine Elms and One Crown Place, while the research also identifies the firm as structural engineer for the future 99 Bishopsgate redevelopment. That last project is particularly significant because its engineering story starts before the replacement tower rises.
Brookfield considered whether the existing 1970s building could be comprehensively retrofitted. The structural constraints ultimately pushed the project towards replacement above ground, but the current engineering strategy targets substantial retention below ground. The research identifies a target to retain around 48% of the existing building's mass through reuse of existing foundation infrastructure.
That makes 99 Bishopsgate neither a conventional refurbishment nor a clean-sheet new build. It represents the increasingly important middle ground: demolish what cannot reasonably be retained, but reuse valuable structural assets where their capacity and condition allow it. The project also features in our wider review of London skyscrapers delayed, redesigned or still waiting to start, where demolition and main structural construction are deliberately treated as separate stages.
Robert Bird Group: Complex Sites Matter as Much as Height
Robert Bird Group appears differently in the research. Its role is strongly associated with complex City projects, construction engineering and difficult structural interfaces rather than simply accumulating the longest list of completed landmark towers. 100 Bishopsgate is a major completed example, while the research also identifies Robert Bird Group in the engineering teams behind future or technically constrained City developments including 85 Gracechurch Street.
That project demonstrates another constraint that rarely appears in a skyscraper rendering: archaeology. The Gracechurch Street site contains important Roman remains, requiring the proposed building and foundation strategy to respond to archaeological assets rather than treating the entire footprint beneath the building as freely available structural territory. For engineers, archaeology can become a structural-grid issue. Move a pile and the load above it has to find another path. Move enough piles and the entire transfer strategy may change.
The Walkie Talkie Proves the Skyline Is Not a Four-Firm Monopoly
20 Fenchurch Street provides an important correction to any simplistic narrative that every major London tower belongs to the same handful of current firms. The structural engineer was Halcrow Yolles / Halcrow Group. The building's unusual form widens as it rises, meaning its upper floors are substantially larger than the footprint at street level. That geometry produces a completely different structural problem from a conventional vertical tower.
Research material reviewed for this analysis records more than 8,000 tonnes of structural steel across roughly 4,500 separate steel sections. Every floor interacts with a changing building geometry, making three-dimensional coordination fundamental to the structural design rather than simply useful for visualisation. Even the Sky Garden roof structure evolved through the construction process, with architectural elements becoming part of the structural solution.
Who Is Engineering London's Next Skyline?
The answer is less concentrated than the completed skyline. The verified research places WSP on One London / 1 Undershaft, AKT II on 99 Bishopsgate, and Robert Bird Group across significant future City engineering work including 85 Gracechurch Street. One London is particularly important because its approved height places it at approximately the same 309.6m scale as The Shard.
The structural concept is radically different. The approved design uses a stepped arrangement and major expressed structural elements at its base rather than attempting to replicate The Shard's tapered hybrid solution. Because it remains a future structure, those details must be treated as design intent rather than as-built fact.
Our London planning pipeline for 2027–2030 shows why this distinction matters: approved towers can remain in demolition, design development and procurement for years before the structural engineer's calculations turn into concrete and steel on site. The future engineering contest is therefore not simply about who is named on the largest number of planning applications. It is about which engineering teams remain attached as projects move through detailed design, procurement, construction engineering and delivery.
Structural Reuse Could Change the Skyline More Than Height
Perhaps the biggest long-term change is not taller buildings. It is engineers being asked to use structures that already exist. 22 Bishopsgate proved that the foundations of an abandoned skyscraper project could become part of a completely different 278m tower. 99 Bishopsgate is targeting significant below-ground retention even though the existing above-ground building cannot simply become the new scheme.
Elsewhere across London, office redevelopment is increasingly retaining frames, slabs, cores, basements or foundations rather than assuming complete demolition. That creates an entirely different engineering process. Before an existing structure can be given another 30, 50 or 60 years of life, engineers may need reliable evidence for:
• concrete strength;
• reinforcement position;
• slab thickness;
• steel grade;
• foundation capacity;
• pile condition;
• historic loading;
• movement;
• hidden alterations;
• and whether the original drawings describe what was actually built.
That is why the current surge in London structural investigation work is closely connected to the future of structural engineering rather than being a separate specialist market. The more structure London retains, the more important physical verification becomes.
How Does a London Skyscraper Actually Stand Up?
Strip away the architecture and most tall-building load paths can be explained relatively simply.
Gravity:
People, furniture, façades, plant and the building's own weight load the floors. The floors transfer those loads into columns, walls and the structural core. If column positions cannot continue vertically (perhaps because a railway tunnel, entrance, public space or different floor use sits below) transfer beams, trusses or slabs redirect those forces into another set of columns. Those vertical elements carry the loads into a raft, piles or another foundation system. The foundations finally transfer the load into the ground.
Wind:
The core, braced frame, megaframe, outriggers, shear walls or diagrid resist lateral forces and prevent excessive sway and rotation.
Movement:
Engineers predict how concrete shrinks and creeps, how steel deflects, how columns shorten, how foundations settle and how the structure changes as each floor is added.
The façade:
It must remain weather-tight while being attached to a frame that moves under temperature, wind, gravity and long-term structural deformation. A skyscraper therefore does not stand still. It is designed to move predictably.
Seven Structural Facts Hidden in London's Skyline
1. 22 Bishopsgate reused the complete previous foundation system.
The new tower had to adapt to infrastructure designed for the abandoned Pinnacle rather than beginning with an empty site.
2. The Leadenhall Building does not rely on a conventional internal concrete stability core.
Its external steel megaframe performs the principal lateral stability role.
3. Part of 22 Bishopsgate's core rose before all of the new foundation work beneath it was complete.
Construction sequencing became part of the structural engineering problem.
4. The Shard changes structural material as it rises.
Its lower, middle and upper sections use different structural approaches rather than one repeated frame.
5. Some London piles are positioned by railway tunnels rather than by the ideal column grid above.
Principal Tower and other constrained sites demonstrate how underground infrastructure can dictate the geometry of a tower hundreds of metres overhead.
6. The Walkie Talkie contains more than 8,000 tonnes of structural steel according to project technical records reviewed.
Its widening geometry means the structural arrangement changes significantly through the height of the building.
7. Tomorrow's tower may start with yesterday's foundations.
Structural reuse is moving from an unusual engineering achievement towards a serious development strategy.
The Friction Layer: Why the Structural Engineer Credit Is Not Always Simple
Even identifying the engineer behind a skyscraper is more complicated than it sounds. A major London tower can involve:
• a concept structural engineer;
• a permanent-works structural engineer;
• a contractor's structural engineer;
• a geotechnical engineer;
• temporary works designers;
• façade engineers;
• wind engineers;
• specialist connection designers;
• independent checking engineers;
• and construction-engineering teams.
One company may design the original planning concept before another develops the permanent structure. A contractor may then introduce a different construction sequence requiring specialist temporary engineering. A steelwork subcontractor may take responsibility for connection design without becoming the structural engineer for the building itself.
The Shard is a useful example. WSP is identified as the permanent structural engineer in the research, while other engineering businesses carried important foundation, temporary works and construction-engineering responsibilities. Those roles are complementary, not contradictory. This is why company counts should be treated as evidence of repeated project involvement rather than a definitive market-share league table.
Quick Answers: London's Structural Engineering Skyline
Who was the structural engineer for The Shard?
WSP, including the Cantor Seinuk structural engineering lineage, is identified as the permanent structural engineer for The Shard.
Who engineered 22 Bishopsgate?
WSP was structural engineer for 22 Bishopsgate, including the complex strategy required to reuse the previous Pinnacle foundations and substantial basement structure.
Who engineered the Leadenhall Building?
Arup provided structural engineering for the Leadenhall Building and its distinctive external steel megaframe.
Who engineered the Walkie Talkie?
Halcrow Yolles / Halcrow Group is identified as structural engineer for 20 Fenchurch Street.
Which structural engineering firm appears most frequently behind London's tallest buildings?
WSP appears most frequently across the major completed and future towers reviewed for this analysis. This is a researched sample rather than a claim of absolute London market share.
Which London skyscraper has one of the most unusual foundation stories?
22 Bishopsgate is exceptional because its structural design incorporated the foundation system left by the abandoned Pinnacle development.
Which London tower has one of the most unusual stability systems?
The Leadenhall Building stands out because its external steel megaframe provides stability without relying on the conventional internal concrete stability core used by many towers.
Who is engineering London's next generation of tall buildings?
The future pipeline is more fragmented. WSP, AKT II and Robert Bird Group all appear on major City schemes in the reviewed project evidence, alongside other specialist engineering teams.
Why are structural engineers increasingly interested in existing foundations?
Reusing foundations or other structural elements can reduce demolition, materials, carbon and programme, but only where their geometry, capacity, condition and interaction with the new structure can be demonstrated.
The Next Engineering Competition Is Underground
London's future towers will continue to compete for height, views, tenants and architectural identity. But structural engineering is moving in another direction at the same time. The questions increasingly being asked are:
Can the existing foundations be reused?
Can the basement remain?
Can a frame take another ten storeys?
Can tonnes of steel or concrete be removed from the design without compromising performance?
Can new loads be transferred around a railway tunnel instead of forcing major infrastructure protection?
Can engineers prove an existing 1980s or 1990s structure has enough capacity for an entirely new commercial future?
Those questions may shape London's next skyline as much as the race to build another 300m tower. The skyscraper that uses the least new structure may eventually be as technically important as the skyscraper that reaches the greatest height.
The Hidden Constant Behind London's Skyline
Architects change, developers change and main contractors compete for each generation of projects. Yet the structural engineering evidence repeatedly returns to a comparatively small group of firms. WSP has the broadest footprint in the sample reviewed. Arup's portfolio contains some of London's most distinctive structural concepts. AKT II is increasingly prominent across complex geometry, residential towers and the future City pipeline. Robert Bird Group repeatedly appears where construction engineering, difficult substructures and highly constrained sites become central to delivery. Historic firms including Yolles and Halcrow helped establish the structural language of earlier Canary Wharf and City towers.
That may be the real secret of London's skyline. The buildings look completely different, but many of the hardest structural decisions pass through a remarkably concentrated engineering community. And increasingly, their most important work is not visible at all. It is underneath the pavement, inside the core, buried in a transfer structure, hidden behind the façade or encoded into a construction sequence that allows thousands of tonnes of structure to move safely from drawing to reality. The full contractor implications, sequencing risks and mitigation strategies are included in today’s London Construction Magazine briefing.
Evidence-Based Summary
Project-level research indicates that WSP appears most frequently across the major London tall buildings reviewed, while Arup, AKT II and Robert Bird Group form a second group with significant completed and future tower involvement. The engineering itself is becoming more varied: 22 Bishopsgate demonstrates large-scale foundation reuse, the Leadenhall Building uses an external steel megaframe instead of a conventional concrete stability core, and future projects increasingly combine new construction with retained structural assets. London's tallest buildings are therefore shaped as much by what exists below ground — foundations, tunnels, archaeology and previous structures — as by the architecture visible above it.
Source Context & Editorial Note
This analysis reflects project information reviewed up to 14 August 2026. The research compared structural-engineer project records, technical case studies, engineering papers, project-team disclosures, contractor information and available planning material across completed, active and future London tall buildings. Structural-engineering attribution has been treated cautiously. Major towers can have separate concept, permanent works, geotechnical, temporary works, construction engineering, steelwork, façade, wind and checking engineers. A company involved in one of those disciplines has not automatically been described as the building's lead structural engineer.
The firm comparison is therefore based on projects where involvement could be established from the reviewed evidence and should not be interpreted as an audited market-share ranking. Where technical sources disagreed on dimensions, storey counts or engineering roles, uncertain figures have either been omitted or described cautiously rather than presented as confirmed. Future-project structural concepts are also subject to design development. An approved structural strategy can still change before detailed design, procurement and construction, particularly where further investigation, contractor input, archaeology, retained structures or below-ground constraints affect the final solution.
| Expert Verification & Authorship: Mihai Chelmus Founder, London Construction Magazine | Construction Testing & Investigation Specialist |
