Affectionately dubbed the ‘Cheese Grater’, the 225-metre Leadenhall Building sits within the City of London’s financial heart, alongside other Arup collaborations such as Lloyd’s building, St Mary Axe (the ‘Gherkin’), and the Pinnacle.

Aiming to unlock the potential of a high rent location, British Land launched an architectural competition in 2001 to double the size of the previous building, maximise lettable space within the constrained plot and bring the new building quickly to market. The design also had to meet a planning objective to preserve views to St Paul’s Cathedral.

The distinctive triangular form defined the height of the ‘City Cluster’ at the time of construction and preserved views of St Paul’s Cathedral. It allowed for a significantly taller building than usual in such a sensitive location, including a 7-storey, public galleria at ground level, without compromising on lettable area. Speed to the market was also critical. We saved months on the construction programme by employing an unconventional ‘bottom up’ demolition strategy, removing upper floors in parallel with new perimeter foundation works.

The Leadenhall Building achieved BREEAM Excellent. In 2024, it was recognised by the Council for Tall Buildings and Urban Habitats for its continuing success 10 years after its completion.

Structure as architecture

The Leadenhall Building was designed to lean away from St Paul’s Cathedral to avoid obscuring the view of the historic monument from Fleet Street. Achieving this was a feat of structural engineering. Because of its shape, the building leant sideways during construction. To counteract this, some of the sloping steel on the side faces was shortened to pull the megaframe back to the vertical. This began when construction of the 48-storey building reached the 19th floor and was repeated every seven storeys.

The Leadenhall building is a skeletal construction, with its steel and connections being on show. The megaframe connections were modelled and refined using 3D software, so the flow of forces through the connections was as efficient as possible.

As well as adding lettable space, the megaframe allowed for an ambitious construction schedule. Being able to rely on accurate machining of the steelwork meant large sections could be prefabricated, greatly reducing the time needed for construction on site. Accurate fabrication also meant that each floor’s table structures could be lifted into position with their services and floors already attached. In all, 85% of the finished building was prefabricated off-site.

The Leadenhall Building. Credit: Thomas Graham
The steel megaframe forms part of the detailed architecture as well as carrying many services.
Sketches of the Leadenhall Building
Sketches of the Leadenhall Building design.
The Leadenhall Building. Credit: Thomas Graham
Being able to rely on accurate machining of the steelwork meant large sections could be prefabricated, greatly reducing the time needed for shimming on site.