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Swiss Re ‘Gherkin’ – Building Access Solution

Bespoke kinetic solutions for unique challenges in architecture

The Challenge

Building maintenance units – BMUs – provide access for cleaning and maintenance and usually run on tracks fitted on a flat roof, where they can be stored out of sight.

The uniquely shaped ‘Gherkin’, designed by Foster + Partners, has no flat roof. So, an equally unique access solution was required; and it had to be one that would not compromise the appearance of the building. This posed a challenge that many considered too difficult.

The Solution

ARX created a completely unique access solution for the instantly recognisable building in the centre of London, affectionately called the ‘Gherkin’.

Our solution allows maintenance staff to access the full external facade of the 160m high building, as well as the interior and exterior of the ceiling of the top floor restaurant. Five bespoke machines and some highly innovative engineering solved this remarkable challenge.

Technical Details

Orbital crane rails
  • Crane rails orbit the building at the 36th floor, supporting and supplying power to three bespoke BMUs (building maintenance units)
  • Two horizontally telescopic booms access the building below by extending 10m outwards and lowering cradles down the curved side
Inside and out
  • The top-floor restaurant and bar is one of the most exclusive dining locations in the capital
  • The interior of the domed roof is accessed via a slewing hydraulic boom
  • The boom is fully articulated to keep the cradle level in all orientations
Reach for the skies
  • Another telescopic mast stretches 33m upwards, enabling the basket to reach the top of the building
  • The five-stage mast folds out from a BMU that also traverses the orbital rail
  • In order to stay facing the building, the entire boom mechanism is mounted on a rotating powered trolley
All about the moves
  • The solution calls on many ‘kinetic architecture’ disciplines
  • The BMU machines have to traverse between internal and external structural and electrical systems – requiring millimetre accuracy and sophisticated control
  • The external BMU machines retract into the 36th-floor garage, and the internal boom hides below the 40th-floor restaurant
Safely hidden from view
  • A transfer carriage retracts the machines back inside a garage area concealed by roller shutter doors
  • Articulated wheels allow the machines to run on both the circular external rails and the straight rails inside the garage
  • Safety edge and infrared detectors prevent door closure on any person or machinery
It's not just cleaning windows
  • A key design element of the Gherkin is its helical cladding, made up of diamond-shaped glass panels
  • The two external cradles are designed to interface with a special glass replacement unit, for removing and installing the panels
  • The glass panels weigh 400kg each and are held securely using vacuum technology

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