52 Lime Street, known as ‘The Scalpel’, is a striking 190-metre office tower in the heart of the City of London, designed by Kohn Pedersen Fox Associates (KPF) for W.R. Berkley as the location of its UK headquarters and to let to tenants. A considered addition to the skyline, the building works in conversation with its neighbours to complement the overall composition of the ‘City Cluster’ whilst improving the public realm at the base with the introduction of a new public plaza.
The simple geometric form of the 35-storey tower is reinforced by partially reflective glass and bright metallic fold lines.
William Pedersen, one of the Founding Partners of KPF, led the early conceptual design stages explains the thinking behind the design:
“At KPF our aspiration, from the earliest days, was to find a way for tall buildings to create a more ‘social’ interaction with the cities that they inhabit. The role of the building within the city is much like the role of an individual at a cocktail party. To have a good party, the individuals can’t stand isolated from each other – they need to generate some form of conversation. Similarly, tall buildings need to find a way to be able to respond and gesture to their context.
“The introduction of tall buildings into the historic centre of the City of London always generates controversy. Yet they are necessary in a modern, progressive, urban environment. London’s town planners recognised this dilemma. Here they elected to cluster the tall buildings together, making a type of pyramidal massing of their collective form. Their intention was to have buildings, each with a strong personality, build to an architectural crescendo. Each is a strong personality. Each speaks to the other with energy and respect.
“What has been created, in effect, is a type of urban drama. Each participant in the dramatic action has been shaped by the necessity of respecting view corridors to St. Pauls Cathedral. Each does it uniquely, but collectively they make an architectural conversation. 52 Lime Street responds by leaning back to respect the view corridor, creating a paired, but mirrored gesture to the Leadenhall Building, which makes for an exceptional urban conversational, one which is theatrical in its nature.
“Giving our building a folded, origami like quality, was the impetus for its form. Affectionately, it has been dubbed ‘the Scalpel.’ As it rises it folds back to mount to a point on the sky. Identified as a unique participant in the group it also joins enthusiastically with its neighbours. On the ground the urban space it forms with the Willis building creates exceptional urban intimacy. As always, we intend for our tall buildings to be social participants in their contexts. Never have we had the opportunity to add one of our tall buildings to a context of such richness and drama.”
Design and form
At the outset of the project, the City Cluster was in its infancy. The City planners were keen maintain the street edge and limit the height on Leadenhall Street, where the existing buildings were all about five storeys tall, to around 10 storeys. Working with the planning authorities, KPF demonstrated the potential for a tall building on the site that would maintain the street edge, preserve protected views of St Paul’s Cathedral and enhance the public realm.
The kinetic views along Fleet Street played an important role. To protect the view of St Paul’s Cathedral, the building needed either to be stepped or inclined behind the dome. The inclined façade offered a calm silhouette among the existing frenetic array of buildings while providing a wider variety of floor plate types and greater efficiencies. The taut, sculptural form reinforces the more formal urban planning interventions at the ground floor which shape the external space adjacent to the neighbouring building while holding the building line along Leadenhall Street. The massing also provides a counterpoint to the surrounding historic buildings including the Grade I listed St Andrew’s Undershaft and the Lloyd’s building which obtained Grade I listing during the design process.
Reflections on glazing
“Given the highly textural structures adjacent to ours, we have chosen to act as a foil to their presence. They are rough, we are smooth. Not only smooth but also reflective. These surrounding structures represent different eras in history. The most venerable being the Grade l-listed St. Andrews Undershaft, directly across from us on Leadenhall. The facade of our structure mirrors its presence. Lloyd’s of London, also an immediate neighbour, is clad in a textured surface of a more aggressive order. The coolness of our response is a perfect foil.” – William Pedersen
“At 52 Lime Street the glazing is an integral part of the architecture, it is both what creates the strong form and what controls the building’s performance. The detailing and specification was crucial to delivering the design intent. The entire mechanical system, internal comfort and energy used are predicated by the glazed façade. The simple form and alignment of panels across the building are underlined by a hidden complexity in geometry, each inclined pane is slightly trapezoidal to ensure verticality of mullions and to align internal planning grids with the angled facade.” – Charles Olsen, Senior Associate Principal at Kohn Pedersen Fox.
Glass was specified to achieve crisp geometry and ensure sharp reflections. The glazing works with the stainless-steel edges to define the building’s strong identity from near and far. The entrance lobby provides a highly-transparent corner, visually linking Lime Street and Leadenhall Street. Jet Mist granite flooring inside the lobby continues, with a different finish, into the external space providing continuity. This space is activated by a constant flow of building occupants and visitors and contains a range of spaces for waiting and informal breakout at both ground and mezzanine levels. An independent coffee shop at ground floor level, overlooking the new public space, will activate and enliven the immediate area.
The office floors
The offset core provides large uninterrupted and virtually column-free floor plates that are efficient to plan for a variety of tenants, with floor-to-ceiling glass optimising daylighting of the office floors and supplying spectacular views across London. Located on the south of the building, the core shades the building to reduce solar gain and provides higher levels of thermal insulation to the building. The façade is specifically designed to suit the internal planning grid for the building. The grid and interior arrangements of floors and ceilings are aligned with the core which the facades intersect at varying angles and inclines. Mullions are rotated to align with the grid and notional partitions, resolving the complex geometry and ensuring floorplates suit a variety of workspace typologies.
Interior spaces, such as the double-height entrance lobby, lift lobbies, lift interiors and washrooms, feature timeless modern design and detailing, using a palette of high-quality natural materials. An illuminated ceiling to the triple-height atrium above the escalators, emulates natural daylight. A sculptural limestone staircase from the entrance lobby was developed in close collaboration with a stone mason.
Creating an energy-efficient glazed building that performs well environmentally required a holistic design approach, from passive design principals to renewables and an economic structure that minimised material used to reduce the emission of CO2 in construction.
The core is located on the south of the building, against the facade. This provides shading to the interior and allowed the project team to insulate the façade most directly affected by solar gain – minimising the demand for air conditioning and significantly reducing energy use. The building achieved an ‘Excellent’ rating under BREEAM 2014 due to this energy-efficient layout paired with careful detailing and specification of the façade, lighting, and mechanical systems. Energy modelling calculated regulated carbon dioxide emissions in operation 25% lower than required by building regulations.
Computational design of floor beams saved 700t of steel, reducing CO2 emissions from construction by 1,300t and vertical core prestressing allowed core walls to be thinner, saving 1,800m3 of concrete and reducing CO2 emissions from construction by 1,000t. Bike parking and showers encourage sustainable commuting and healthy habits.
The Woodford Stones
Four allegorical stone relief panels – the Woodford Stones – representing the classical elements of earth, air, fire and water have been incorporated in the façade of 52 Lime Street. Commissioned from the renowned sculptor James Woodford for the previous Lloyd’s building, which opened in 1957, the stones were moved to the party wall of 52-54 Lime Street as a part of the planning conditions for the Willis Building, which completed in 2008, and relocated to 52 Lime Street as part of the new development.
This article was originally published in IGS Magazines Winter 2020 Issue: Read the full Magazine here for more thought-leadership from those spearheading the industry
Cover image: Antoine Buchet
About Kohn Pedersen Fox Associates
Kohn Pedersen Fox Associates (KPF) is one of the world’s preeminent architecture firms, providing architecture, interior, programming and master planning services for clients that include some of the most forward-thinking developers, corporations, entrepreneurs, and institutions in the United States and around the world. The firm’s extensive portfolio spans more than 40 countries and includes a wide range of projects from office and residential buildings to civic and cultural spaces to educational facilities. Driven by individual design solutions, rather than a predetermined style, KPF’s mission is to create buildings and places of the utmost quality and contextual sensitivity, providing a valuable impact on the cities they inhabit.
As a global practice with a far-reaching impact, KPF endeavors to design lasting architectural solutions that mitigate their lifecycle impact on environmental resources and that protect and enhance the wellbeing of the communities they serve. For that reason, the firm has joined AIA, RIBA, and many of its peers in a joint effort to develop the capabilities to design and deliver carbon-neutral buildings by 2030.
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