London 'Gherkin'

30 St Mary Axe (The Gherkin)

30 St Mary Axe

30 St Mary Axe, also known as the Gherkin and the Swiss Re Building, is a skyscraper in London's main financial district, the City of London, completed in December 2003 and opened on 28 April 2004. It is 180 metres (591 ft) tall, with 40 floors. Its construction symbolised the start of a new high-rise construction boom in London.

The building was designed by Lord Foster, his then partner Ken Shuttleworth, and Arup engineers, and was constructed by Skanska of Sweden in 2001–2004.

History of the site

The building is on the former site of the Baltic Exchange building, the headquarters of a global marketplace for ship sales and shipping information. On 10 April 1992 the Provisional IRA detonated a bomb close to the Exchange, severely damaging the historic Exchange building and neighbouring structures.

The UK government's statutory adviser on the historic environment, English Heritage, and the City of London governing body, the City of London Corporation, insisted that any redevelopment must restore the building's old façade onto St Mary Axe. The Exchange Hall was a celebrated fixture of the ship trading company.

Baltic Exchange, being unable to afford such an undertaking, sold the land to Trafalgar House in 1995. Most of the remaining structures on the site were then carefully dismantled; the interior of Exchange Hall and the façade were preserved and sealed from the elements.

After English Heritage later discovered the damage was far more severe than previously thought, they stopped insisting on full restoration, albeit over the objections of the architectural conservationists who favoured reconstruction.

Origin of "Gherkin" nickname

In 1996 Trafalgar House submitted plans for the Millennium Tower, a 386 metres (1,266 ft) building with more than 90,000 m² (1 million ft²) office space, and public viewing platform at 305 m (1,000 ft). This plan was dropped after objections; the revised plan for a lower tower was accepted.

Looking south down Bishopsgate, one of the main roads leading through London's financial district.

The gherkin name dates back to at least 1999, referring to that plan's highly unorthodox layout.

The planning process

On 23 August 2000, Deputy Prime Minister John Prescott granted planning permission to construct a building much larger than the old Exchange on the site.

The site was special because it needed development, was not on any of the "sight lines" (planning guidance requires that new buildings do not obstruct or detract from the view of St Paul's dome when viewed from a number of locations around London), and it had housed the Baltic Exchange.

The plan for the site was to reconstruct the Baltic Exchange. GMW Architects proposed building a new rectangular building surrounding a restored exchange — the square shape would have the type of large floor plan that banks liked.

Eventually, the planners realised that the exchange was not recoverable, forcing them to relax their building constraints; they hinted that an "architecturally significant" building might pass favourably with city authorities. This move opened up the architect to design freely; it eliminated the restrictive demands for a large, capital-efficient, money-making building that favoured the client.

Another major influence during the project's gestation was Canary Wharf. At the time, banks and commercial institutions were moving to Canary Wharf, because the area allowed buildings with modern, large floor plans. The City of London was not approving such buildings, forcing firms to disperse their staff across many sites. When the city realised the mass defection its policies were causing, it relaxed its opposition to high-rise buildings.

Swiss Re's low level plan met the planning authority's desire to maintain London's traditional streetscape with its relatively narrow streets. The mass of the Swiss Re tower was not too imposing. Like Barclays Bank's former City headquarters, the passerby is nearly oblivious to the tower's existence in neighbouring streets until directly underneath it. Such planning rules/goals create a city's visual identity — e.g. New York City's plot ratio and setback rules have had an enormous impact on how it looks compared to cities with more conservative rules like London and Paris.

Design and construction

The base of the tower

The building was constructed by Skanska, completed in December 2003 and opened on 28 April 2004.

Work in progress on the 'Gherkin'. Construction began in March 2001

The building uses energy-saving methods which allow it to use half the power a similar tower would typically consume. Gaps in each floor create six shafts that serve as a natural ventilation system for the entire building even though required firebreaks on every sixth floor interrupt the "chimney." The shafts create a giant double glazing effect; air is sandwiched between two layers of glazing and insulates the office space inside.

Architects limit double glazing in residential houses to avoid the inefficient convection of heat, but the Swiss Re tower exploits this effect. The shafts pull warm air out of the building during the summer and warm the building in the winter using passive solar heating. The shafts also allow sunlight to pass through the building, making the work environment more pleasing, and keeping the lighting costs down.

Design of the tower contrasts against other buildings

The primary methods for controlling wind-excited sways are to increase the stiffness, or increase damping with tuned/active mass dampers. To a design by Arup, Swiss Re's fully triangulated perimeter structure makes the building sufficiently stiff without any extra reinforcements.

Despite its overall curved glass shape, there is only one piece of curved glass on the building — the lens-shaped cap at the very top.

The primary occupant of the building is Swiss Re, a global reinsurance company, who had the building commissioned as the head office for their UK operation. As owners, their company name lends itself to another nickname for the building variants on Swiss Re Tower, although this has never been an official title.

On the building's top level (the 40th floor), there is a bar for tenants and their guests featuring a 360° view of London. A restaurant operates on the 39th floor, and private dining rooms on the 38th.

Whereas most buildings have extensive lift equipment on the roof of the building, this was not possible for the Gherkin since a bar had been planned for the 40th floor. The architects dealt with this by having the main lift only reach the 34th floor, and then having a push-from-below lift to the 39th floor. There is a marble stairwell and a disabled persons' lift which leads the visitor up to the bar in the dome.

The building is visible over long distances: from the north for instance, it can be seen from the M11 motorway some 20 miles (32 km) away while to the west it can be seen from the statue of George III in Windsor Great Park. The view from the A10 has been obscured by the new buildings on Bishopsgate

After completion

Skyline view with Tower 42, the Willis Building, 30 St Mary Axe and the Broadgate Tower.

On 25 April 2005, the press reported that a glass panel two thirds up the 590 ft (180 m) tower had fallen to the plaza beneath on 18 April. The plaza was sealed off, but the building remained open. A temporary covered walkway, extending across the plaza to the building's reception, was erected to protect visitors. Engineers examined the other 744 glass panels on the building.

In December 2005, the building was voted the most admired new building in the world, in a survey of the world's largest firms of architects, as published in 2006 BD World Architecture 200.

In September 2006, the building was put up for sale with a price tag of GB£600 million. Potential buyers included British Land, Land Securities, Prudential, ING and the Abu Dhabi royal family. The 40-story skyscraper, when fully let, would have a potential annual income of GB£27 million. In December 2006 it was suggested that IVG Asticus, controlled by the German property firm, IVG Immobilien AG, had become the new owners of 30 St Mary Axe.

On 21 February 2007, IVG Immobilien AG and UK investment firm Evans Randall completed their joint purchase of the building for GB£30 million (approx. US$1.26 billion c. 2007).