On Top of the City: Behind the Scenes at the Leadenhall Building

Settled comfortably around a black conference table – the only item of furniture in an office space still lacking its carpet tiles – on the 40th floor of the new Leadenhall Building, I had the opportunity to discuss with lead designer Graham Stirk and his partner, practice co-founder Richard Rogers, the forces that shaped their new building and how they came to be working in the City of London once again.

Rogers Stirk Harbour + Partners has a rich presence in the Square Mile, including the landmark Lloyd’s of London, standing directly opposite the Leadenhall Building. The firm has specialised in assured, sometimes assertive insertions within the City’s fine, historic urban grain, and so setting aside the sheer bravura of the 52-story, 225 meter skyscraper, with its sloping glass façade to the south (giving it the popular nickname of the Cheesegrater) the first question that arose was a simple one – how did the building come about?

Graham Stirk, seated centre in dark jacket, and Richard Rogers discussing the Leadenhall Building in the 40th floor marketing suite. Image © Chris Rogers

Developer British Land held a limited competition to replace the admired but outdated former P&O tower at 122 Leadenhall Street with a new building, one likely to attract the insurance businesses that have made this very specific area of the City their preferred location. “All the negotiations are done at ground level, the signing on the upper floors,” quips Stirk.

Without a pre-let, occupiable area was everything and so RSHP’s winning scheme, though promising, was ultimately rejected. Both height and servicing were clearly the key to unlocking the maximum potential of the site, and through a fresh look at applicable height rules and further exploration of form with planners, the current profile emerged.

Detail of K-Bracing at the top of the Leadenhall Building. Image © Richard Bryant – Courtesy of British Land/Oxford Properties

It was, says Stirk, about discovering “how we could swing all of the mass away from the southern site boundary” while still attaining a distinctive yet visually coherent shape for the new building, something absent in earlier iterations. To make this possible, work with Arup generated the concept of the building's megaframe. These cage-like modules formed by a perimeter of steel beams up to 28 metres long are placed one on top of the other to create the final structure. Further steel pieces in the shape of a letter K are stacked horizontally to form the ladder frames visible at the two northern corners. The north core houses the lifts, toilets, risers and local plant.

The need to pull the top of the building so much higher, says Stirk, made British Land amenable to moving the usual functions of a tower’s ground floor – lobby, security, lifts – up higher as well, to a point where they are suspended from the fifth floor level. This audacious move allowed for a ground floor that is in fact a continuation of Leadenhall Street and is landscaped as part of the street rather than part of the building. It is defined by the points where the raking megaframe beams touch the ground. A pair of escalators, offset from each other in height and plan, suggest double-deck lifts, but in fact one services a dedicated reception for principal tenant Aon, who – in a sign of quick acceptance – is moving its world headquarters here from Chicago.

The eastern portion of the ground floor 'lobby' of the Leadenhall Building, as seen from the second floor reception area. The connection with St Helen's Square has yet to be made. Note the V shapes formed by the columns of the megaframes. Image © Richard Bryant – Courtesy of British Land/Oxford Properties

Stirk is keen to point out that the connectivity between here and the adjacent St Helen’s Square originally made with the P&O building is not yet complete, but that there is still “a sense of the space” that will eventually appear. “Rather than create a podium, we’ve created a cut,” says Stirk of this space. Required by planners to respect the cornice line of the neighbouring Lutyens facade, which is achieved by a projecting canopy that also mitigates downdraft, Stirk was personally concerned about giving something back to the street scene. He therefore sought to bring “a level of depth and complexity” to this part of the building, “a texture rather than an expanse of 200mm glazing wrapped around it.”

Defining a street by a negative, as Stirk puts it, may seem counter-intuitive but it has an obvious and highly successful precedent in the Seagram Building in New York, and the plaza it created for the city. Stirk also sought to emulate buildings in the City of London where voids around their perimeter are as vital as solids, such as Wren’s cathedral, Leadenhall market nearby and of course Lloyd’s of London, fortuitously – and magnificently – framed when ascending or descending the Leadenhall Building’s escalators.

Lloyd's of London seen from the escalators, with the fifth floor wind canopy of the Leadenhall Building and its megaframes. Image © Chris Rogers

Unsurprisingly, Lloyd’s was also prominent in our discussion about the search for an appropriate overall expression for the new building.

At the heart of that quest, said Stirk, was the difference between a commissioned building like Lloyd’s and a speculative one like the Leadenhall Building. The latter has no ‘branding’ during its life, and must appeal to many possible occupiers. Richard Rogers summarised this as Lloyd’s wanting privacy and history, but British Land a public and open face, and volume.

The Leadenhall Building therefore became “an externalised expression of a neutral area.” The coloured toilets (blue for men, red for women) inserted into areas of the north core not occupied by lifts constituted “an architectural language of supergraphics” for that façade, given further expression by the orange and green frames of the glass lift cars and the yellow of their shafts. All three colours, according to Stirk and project architect Andy Young, originating from their love of 1970s Italian sportscars. The diagrid structure of the megaframes and ladder frames – plain to see yet meticulously designed – has its own cadence and feel, and operates above the supergraphics for a layered effect.

The northern support core of the Leadenhall Building. Image © Richard Bryant – Courtesy of British Land/Oxford Properties

Notwithstanding their differences, both Lloyd’s and the Leadenhall Building are part of the same lineage, maintained Stirk. “There is a relationship, just in a different way. It’s a form of thinking, not an aesthetic. That might result in a particular look, but it’s driven by each job.”

The physical process of achieving this was well documented in the recent television documentary Superskycrapers. Around 85% of the building was prefabricated, partly a pragmatic response to a constricted site, but also a direct result of the evolution of construction technology. No wet trade work was involved above the foundations, all 52 floors erected using only steel and pre-cast reinforced concrete plates. As Stirk said in response to my question about the extent of pure research at RSHP, much technical advancement actually comes via partner sub-contractors, exploring “what can be deformed, bent, pushed to solve a particular problem.” The practice’s architecture thus celebrates and is in turn driven by “the joy of people being involved in technology that is visible.” My follow up comment placing RSHP firmly in the line of British constructional engineering begun by metalworker Abraham Darby III in Coalbrookdale, Shropshire two centuries before seems to go well with Rogers. “That,” he nodded quietly, “is our language.”

If so, then what to make of their new essay?

Courtesy of Rogers Stirk Harbour + Partners

A full assessment of the ground floor “lobby”, as Stirk calls it despite its alfresco nature, should await completion of the work in 2015, but early impressions can be valuable. Any amount of greenery in the City must be given an unqualified welcome, of course, and the trees and grass are a very rare delight and should genuinely blur the boundaries between street and lobby. The space did feel enclosed, though, and dark, even on a bright September morning, not helped by the battleship grey finish of the steel and the ‘off-black’ granite floor. It’s an impression confirmed by the big ventilation ‘funnels’, as they are termed, and the tough hydrants, both of which thrust out of the ground to confront the visitor. Comparison with SOM’s recent Broadgate Tower is instructive, where stainless steel cladding makes a far brighter impression. The slope of the land down to the north-south passageway is a little intimidating, too, though cheeringly recalling a previous generation of post-war buildings, threaded through with intriguing pedways.

But perhaps this will change when the space is fully occupied and animated by those people shown in British Land’s newsletter visualisation, with their bright clothing and hairstyles. It will also be fascinating to see whether the invitation for people to come and use the space is honoured; certainly the private nature of the space is made emphatic by the closely-spaced rank of bollards immediately within the building’s curtilage.

View of and through lift shafts in the Leadenhall Building. Image © Chris Rogers

Close-up, though, that delight in the visible and the crafted of which Stirk spoke is evident. The connectors on the escalator hangers, the fat bolts of the megaframe downstands, the exposed but very carefully detailed ceiling - all bring interest and tactility. This precise, machined, component-based architecture, also seen in the attractively purposeful ladder frames, is reminiscent of Lloyd’s of course, but also the practice’s Reuters Data Centre in London’s dockland, completed over twenty years ago. Approaching from the north, the service core presents a wonderfully intricate and absorbing display: now moving, now still, a delicate mechanism on a grand scale like an abacus operated by a giant. That the lifts are encased in smooth glass allows them to be read as a ripple of activity beneath a placid surface, and the cluster of hydraulic buffers at their bases – the lift ‘pits’, daringly raised well above head height to enable the pedestrian passage below – irresistibly recall children’s construction toy parts.“It’s like a big stained glass building,” said Stirk, happily, of his colourful spectacle.

Inside the second floor reception, black dividers (concealing digital information displays) and gloss black security barriers continue the brooding quality seen below. It is, then, a long and compressive walk from this dark space, through the narrow link between the main block and the north core and out, finally, into the tall lift lobbies, where the view expands dramatically in a rhythm of vertical slices, yellow steel and epic views. During the impressive ascent in the world’s fastest lifts, the entire city unfolds to thrilling effect, but actually the entire progression through the building is energetic and exciting, moving as one does from the street, into the lobby, up to reception, through to the rear of the building, up a wall of glass lifts and to the top floor, only to then traverse the depth of the block once more in reverse, to come back to the front.

Floor 45, the highest office level of the Leadenhall Building and the highest such space in London. Note the 'tree' columns. Image © Paul Raftery

The 45th floor is the smallest office story but, with its double height and powerful metal 'trees', is particularly dramatic and the highest workspace in London. Arguably even more impressive is floor 48. A paved surface, spotlessly clean at present, is effectively a mezzanine to the storey below but with the glazing just a metre or so in front due to the inclined plane of the façade. Further levels are glimpsed above our heads, and behind, four immense red boxes house emergency power generators capable of sustaining the entire building at full occupancy. The whole scene thrillingly recalls Fritz Lang’s Metropolis, or the promenade deck of some super-Zeppelin floating airily above the city. Both Stirk and Rogers would be quick to deny that any change in the fundamental tenets they set out three and a half decades ago has occurred. And if the built language of the City and the firm is characterised by both continuity and change, the Leadenhall Building makes the point eloquently enough on its own.

Floor 48, the lowest of four plant storeys that fill the top-most megaframe module. Image © Chris Rogers

Chris Rogers writes on architecture and visual culture. A longer version of this article can be found on his site.

About this author
Cite: Chris Rogers. "On Top of the City: Behind the Scenes at the Leadenhall Building" 16 Sep 2014. ArchDaily. Accessed . <https://www.archdaily.com/548696/top-of-the-city-the-leadenhall-building-inside-and-out> ISSN 0719-8884

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