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Tower 42 (NatWest Tower)
Bishopsgate, City of London, UK
Tower 42 (NatWest Tower)
associated engineer
Wilem William Frischmann
Pell Frischmann
date  1971 - 1980, opened 11th June 1981
era  Modern  |  category  Building  |  reference  TQ329813
ICE reference number  HEW 2374
photo  Jane Joyce
Tower 42, formerly the National Westminster Tower (NatWest Tower), was Britain’s tallest building for a decade until the completion of Canary Wharf Tower. The central core of its structure supports three cantilevered leaves, creating the tower’s distinctive 12-sided plan shape and making it the world’s tallest cantilevered structure at the time. The tower provides office accommodation and was refurbished following extensive bomb damage by a terrorist attack in Bishopsgate.
The location selected for the tower is a roughly triangular piece of land 10,750 sq m in area, occupied originally by buildings belonging to the National Provincial Bank. The project began in May 1963, when the bank’s architecture department applied for outline planning permission to develop the site. This was granted in November 1964. However, the Control of Office & Industrial Development Act 1965 halted the scheme until an office development permit was issued in June 1968.
British architect Richard Seifert (1910-2001) was appointed to design the tower. He is often cited as the person who introduced high-rise buildings into UK cities, transforming urban skylines forever. The tower he created here, with its curving façades and staggered silhouette provides a dramatic contrast with the shorter rectilinear office blocks of the period.
In January 1970, banking organisations owned by the National Provincial, the District and the Westminster merged to become the National Westminster Bank. The new flagship tower would be known as the National Westminster, or NatWest, Tower.
At a proposed 198m, it was to be London’s tallest building. Seifert courted controversy by suggesting the nearby Grade I listed Banking Hall (completed 1865), designed by John Gibson (1817-92), and City Club of London (1834), by Philip Hardwick (1792-1870), be demolished as part of the project. He also offered an alternative design with two towers, of 56m and 152m.
Public opinion favoured a single tower of 183m, and Gibson Hall was saved by a preservation order. Planning approval was granted in May 1970 and site clearance began the same year. Construction commenced in 1971. In February 1974, with work already well underway, the City of London Club became a Grade II* listed building and its agreed demolition as part of the project was refused.
The complexity of the site, the problem of founding such a large building in London clay and the mechanical services requirements of the tower all precluded a simple structural solution. Research and assessment undertaken to inform the project during the design stage included structural modelling, investigation of dynamic stability and finite element analysis of the foundations.
Work began with the excavation of a pit more than 16m below ground level, surrounded by retaining walls of contiguous bored piles restrained with ground anchors. Bearing piles for the tower’s foundations were installed from a mobile crane lowered into the pit. In total, there are 375 closely spaced bored piles of reinforced concrete. Each one is 25m deep and generally 1.2m in diameter, widening to 2.4m diameter at its base.
Above the piles, the building sits on a circular foundation raft of heavily reinforced concrete, 54m in diameter and 4.5m thick. The tower’s central core is supported on a plinth constructed on the raft, and has a stylised trefoil shape in plan.
The challenge of working around the extensive reinforcement for the core wall led to the development of a new method of slipforming in concrete. Other innovations during construction included the use of lasers to ensure vertical alignment of the tower and CCTV cameras for assisting tower crane operators.
The tower’s basement houses car parking and delivery access. The building has three entry levels — from the street, at podium level and via a mezzanine entrance.
The core contains elevators, stairs and lavatories with plant rooms, services and a cooling tower at the top. Its office floors are arranged in three distinct leaves cantilevered some 9m from the core. The cantilevers support the leaf structures and consist of heavy reinforced concrete cellular beams. Above these, a structural steel frame surrounds the core. The floors are of lightweight composite construction.
The tower has 42 cantilevered storeys. The lowest is designated Level 1, though it is actually four floors above ground. The core rises above the office roofs to Level 46. Moving clockwise around the core from Old Broad Street, the bases of successive leaves step up by two levels and their tops down by the same amount, giving leaves of differing heights. Only levels 5 to 38 wrap around the whole building.
Intermediate plant floors at Levels 13, 22 and 31 service the office floors above and below. Levels 23 and 24 have sky lobbies for lift passengers to interchange between express and local elevators. The building has more than 20 elevators, some with a top speed of 7m/s (equivalent to 25kph or 15.7mph).
The building showcased many design features previously unseen in Britain at the time, such as double-deck elevators, a mechanised internal delivery system for distributing mail and documents, automated window washing by robotic apparatus, gas turbine standby generators and computer-controlled air conditioning, lighting, security and lift operation.
The façade was finished in bronze-coloured single glazing with closely spaced mullions in the form of stainless steel ribs that emphasise its height. The exposed top of the core has similar vertical ribbing of equally high-quality stainless steel. The building’s three leaves give the building an irregular 12-sided plan shape. Viewed from above, the arrangement of core and leaves appears to echo the company logo of bank, though Seifert always denied the similarity.
By April 1980, the completed tower was in use. It had cost around £72m to construct and was opened by Queen Elizabeth II on 11th June 1981. Though a prestigious landmark structure, it could not accommodate all the bank’s operations and it soon became used only for the international banking division. The shape of the leaves, the lack of column-free space and the restricted ceiling heights resulting from the core and cantilever design all constrained the flexibility of the internal layout. Each leaf has an area of only 279 sq m per floor.
On 27th October 1986, the so-called Big Bang deregulation of financial markets resulted in financial services organisations requiring large open trading floors, impossible in a narrow tower. NatWest subsequently relocated its headquarters to 41 Lothbury (TQ327812).
The NatWest Tower was Britain’s tallest building until 1990, when Canary Wharf Tower (TQ375803) at 1 Canada Square in London’s Docklands was topped out. Its architect was Cesar Pelli (b.1926).
On 24th April 1993, the NatWest Tower was badly damaged by a terrorist bomb detonated in the Bishopsgate area of the City of London. Most of the tower’s single glazing was destroyed by the blast.
From 1994, GMW Architects worked with Seifert’s son John on a programme of renovation, which was completed by 1998, at a cost of £75m. Restoration maintained the appearance of the elevations but the interior was refurbished. Works included the installation of double glazing, the replacement of building services and the removal of air handling units from the office floors to provide more useable space. At ground level, a huge upswept glass canopy with triple-height atrium replaces the original entrance lobby.
The tower reopened as the International Financial Centre, but was soon sold by NatWest. In 1998, it was renamed Tower 42 by the new owners, Tower Limited Partnership (a consortium of Merrill Lynch and Hermes Property Ltd). The building was marketed as offering luxury serviced offices for tenants requiring smaller premises. A restaurant and champagne bar was installed on the top floor giving its patrons views across central London. It remains one of the few skyscrapers in London that offers public access to its summit.
In 2004-8, further refurbishment was carried out, including landscaping, pedestrian spaces and new restaurants. In 2011, South African businessman Nathan Kirsh (b.1932) purchased Tower 42 for £282.5m.
In June 2012, an LED multimedia lighting system was installed on levels 39-42 to replace the high-energy-use floodlights at the top of the building. The tower’s exterior was clad with thousands of pixels mounted on chain netting, which display various lighting designs and colours, including the Olympic rings during the London 2012 Olympic and Paralympic Games.
On 1st October 2014, the tower was refused listed building status on account of its alterations — the removal of original interior fittings, the construction of a new entrance, and the cladding and glazing replacement all counted against its heritage recognition.
Commissioned by: National Westminster Bank
Architect: Richard Seifert & Partners
Architect (1994-8): GMW Architects
Architect (2004-8): Fletcher Priest Architects
Contractor (1971-80): John Mowlem & Co Ltd
Steelwork (1971-80): Cleveland Bridge Ltd
Research: ECPK
bibliography
ttp://postwarbuildings.com
http://skyscrapercenter.com
www.architectsjournal.co.uk/news
www.architecture.com
www.building.co.uk
www.chrismrogers.net
www.cityoflondonclub.com
www.e-architect.co.uk
www.gibsonhall.com
www.historicengland.org.uk
www.ice.org
www.insider-london.co.uk
www.skyscrapernews.com
www.svma.co.uk
www.tallestskyscrapers.info
www.tower42.com
reference sources   CEH Lond
Location

Tower 42 (NatWest Tower)