Now you see it... The Cheesegrater's disappearing act

How times have changed. Nearly 30 years ago Lloyds of London was commissioned as the future-looking bespoke HQ of one of the world’s most famous financial institutions, which with its insides all on the outside, was nothing less than a visceral expression of the game changing nature of the financial Big Bang itself. Once completed in 1986, its service cores – fashioned from stainless steel as an exquisite exoskeleton for the building – lorded it for years over the Square Mile like the towers of San Gimignano over its medieval centre. With all the services moved to the perimeter, architect Richard Rogers argued, occupiers of the doughnut-shaped floor plates within were free to expand or contract as needs demanded. Given what’s happened to the financial markets since then, it was a strategy that was right on the money.

But the realisation that markets could implode as well as explode didn’t dampen thinking in the 1990s. The City saw its dominance threatened not only by Canary Wharf, rising Phoenix-like from the ashes of Olympia & York’s doomed investment, but by competition from Frankfurt in a reunified, and economically strong Germany. City of London chief planner Peter Rees had been charged in 1985 with supplying a projected 10m ft2 of office space, while heading his own crusade to ‘sex up’ the Square Mile after hours. In the 28 years under racy Rees’ tenure it has not only grown upwards, but transformed from a place where you could hear pins drop to one where you can see pints sunk. A Friday night spent in one of its huge, new, testosterone-fuelled and stiletto-tipped megabars is evidence enough that the planner realised his goal of putting the sex back in The City.

The Leadenhall building by Rogers Stirk Harbour and Partners feels very much part of this period of reinvention, despite having been put on hold between 2007-10 as British Land waited for the damaged economy to recover. At nearly 85,000m2, it rises to 225m and 50 storeys in the east side of the City, dwarfing the adjacent Lloyd’s Building. The yellow steel structure of its north core, offset by a succession of red and blue toilet pods, it appears as a Brobdingnagian thermometer, callibrating the City’s cultural shift from ‘old boys’ to ‘wide boys’. Although driven by a 50% pre-let with insurance firm AON, by way of a reality check the first public images of Leadenhall that I saw were in a Tube ad for serviced office provider Servcorp, which has leased 12,000ft2 on Level 30. Rees might claim credit for the moniker ‘Cheese­grater’, but the form was influenced most strongly by the St Paul’s viewing corridors and how RSHP resolved the tower’s geometry so as not to impinge on the cathedral as seen from the west. As a result, the sleek ‘A’-shaped glazed steel megaframe leans deferentially back from St Paul’s nave walls to mask its wedge-like form in the building line as seen from Fleet St’s ‘Ye Olde Cheshire Cheese’ pub – leaving the lion’s share of the skyline to Wren’s dome.

Strangely, for the second tallest building in the City, the tower creeps up on you at ground level too – certainly on Leadenhall St. This is due partly to the fact that as well as disappearing like the Cheshire Cat when you’re walking down Fleet St, the architect resolved the building’s interface with the ground by cleverly doing away with most of it. It’s here that you’ll find the structure most clearly expressed – the huge steel columns of the tapered south elevation shooting free of the 1.3m thick double-skin ventilated cavity facade at 28m up and driving down into the edges of the site defining the four storey basement box below. This dematerialisation of the building at lower levels, short of the exterior escalators to the stacked AON and tenant lobbies is an ingenious move. Not only does it deal with how a 50 storey tower handles the nearness of the seven storey Lutyens building next door, it also gives the north facade of the Lloyds Building space to breathe. 

It also defines the major spatial move of the development – the sizeable open ‘Galleria’ beneath the tower that will be merged with the existing St Helen’s Square – as well as a new route north through the building to connect St Helen’s Bishopsgate to the north with St Andrew’s Undershaft  and the Gherkin. One could (and should) debate the pros and cons of stealth privatisation of the public realm via private funding, but this new plaza area reinforces RSHP’s spatial commitment to a sense of public realm which it has championed since the Place Pompidou. And while there’s something divisive about the glass screens popping up from the plaza to counter the worst wind eddies, the 20,000ft2 park creates an area that’s coherent and, with its narrow under-tower link, nuanced.

Leadenhall’s structure marks a development in RSHP’s formal language and its approach to the office typology. Where the 1986 owner-occupied Lloyds consisted of concrete floor plates with a central atrium, concrete structure and steel cores, the 1999 spec Daiwa building at 88 Wood Street had solid floor plates, concrete floors, steel structure and glazed perimeter service cores. Here there are no such appendages to the floor plates. The steel wedge form is all; defining both the office floor and the line of the north core within its geometry. The latter is less a simple core than a whole wall of 22 lifts, 82 washrooms, 45 lobbies and top down/bottom up plant servicing. It’s all exposed: lifts and counterweights in orange or green, their motors visible above the shafts as if in display vitrines; columns and diaphragm structure in yellow as well as toilet pods. With male and female banks denoted in blue and red, these were pre-fabricated in Northern Ireland, brought in on the back of a lorry, lifted and bolted into place. The arrangement of low, mid and high rise lifts means that as banks fall away, they’re gradually exposed on the north core, giving a layered delicacy to this face. They also give rise to naturally lit washrooms – rare for the spec office typology – some experiencing the sexy swoosh of the lifts passing their translucent glazed faces.

Arup Associate director Damian Eley says the engineering strategy for Leadenhall meant balancing cost and buildability with RSHP’s architectural intent for expressed structure. With no concrete cores to rely on, fundamental to the asymmetrical form’s stability was the 6000 tonne steel megaframe. This perimeter structure is formed of seven-storey sections, bounded at top and bottom with horizontal steels, braced by diagonal ones and connected every 28m back to the K-bracing of the fire fighting cores at the rear of the floor plate on the east and west sides. Eight of these, tapering back at a 10º angle, are stacked on top of each other to create the huge wedge-shaped form. The K-bracing gives lateral stiffness to floors and together with the megaframe’s columns and bracing, anchors the whole thing to the ground. You might argue that such a deliberate and eccentrically-shaped form is counter-intuitive from an engineering perspective; perhaps it is, but its rigidity is such that even the north core, with its yellow columns and horizontal steel diaphragm – holding lifts, lobbies and vertical services – gains all its structural stability from it. 

Main floor plates meanwhile get further support from six internal columns – transferring loads down – which disappear in succession as the floors recede upwards. The two columns left at Level 45 perform one additional function at the apex of the tower – to resist the tendency for the structure to expand and contract, which is particularly marked on the south face when the sun heats the steel. Here they branch at the treetops into diagonal bracing, reaching up to join the primary north and south steelwork and hold the megaframe in place by resisting the thermal movement of the stretching and contracting structure. It’s a simple form realised by what appears to be some devilishly complex engineering.

Being part of the syzygy of Rafael Viñoly’s 20 Fenchurch St and Renzo Piano’s Shard across the Thames, the alliance also begs comparison of the three and Leadenhall holds its own admirably. Full fit-out is yet to take place, but the shell and core approaches for this essentially speculative development bear up well to scrutiny. Reception areas are generous, darkly fitted-out and understated, with common lobbies and washrooms crisply detailed and taking full advantage of their perimeter positioning. The building cost came in at £2700/m2. Project architect Andy Young called it ‘unbelievably cheap. Accounting for inflation it’s the same sum of money to build this today as it cost to build Lloyd’s in 1986. That’s how efficient this building is.’ 

Initially a casualty of the economic downturn, it has a sense of being austerity architecture but in a bold guise, that in the intervening years has been value-engineered and pared back in a way that seems to have enhanced rather than detracted from the functionalist expression. This ‘boxing-in’ of the floor plate and services within an all-encompassing glazed skin might intially have been generated by RSHP through cost concerns, but it harks back to the proto high tech that started it all: like the modulated red marble facade of Franco Albini’s 1961 Rinascente in Rome that so enamoured Reyner Banham, its services hinted-at behind its rippled stone skin. With RSHP’s recent solidly-expressed British Museum WCEC extension, it seems to suggest the firm is returning to these early, more constrained high tech roots for inspiration.

Leadenhall seems to have a sense of being both public-spirited and state-of-the-art in a way that belies the straightened times in which it was procured. That deferential cutting away at ground level also gives the street room to breathe, while its smoothly running lifts are now the fastest in the world. One can only assume that Peter Rees, now professor at The Bartlett – a school reinvented by a member of Archigram, is pleased. ‘I like tall buildings because you have more time to make love in the lift,’ he pruriently remarked to the Evening Standard on stepping down earlier this year. I suggest he gird his loins – here he’ll have just over 20 seconds…