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Making a mark

Credits

'Reticent and anonymous' - Pevsner's verdict on the former Winchester House at the eastern end of London Wall - is a description which could well be applied to much of the commercial architecture built in the City of London in the 1950s, 60s and even beyond. The occasional grandiloquent gesture aside - Lutyens' Midland Bank or Rogers' Lloyd's, for example - City institutions have been canny, cautious and unimaginative clients over the last 150 years. Winchester House, completed in 1968 and consisting of a 22-storey office tower set on a podium, was, in fact, mean, dull and utterly at odds with its surroundings. Its replacement by a building which is conspicuously well-crafted and makes a sincere effort to enhance the public domain, without any concession to neo-historicism, must therefore be a progressive move and a matter for some celebration.

For David Walker, architectural design director of Swanke Hayden Connell Architects (shca), the recently completed Winchester House project has further significance - 'this is what we came to London to do', says Walker. shca was one of a number of American practices which set up shop in London in the aftermath of the Big Bang. Yale-trained Walker arrived in London in 1988, but it is only with Winchester House, a project which has extended over a decade, and the forthcoming - and massive - European headquarters for Merrill Lynch at Newgate that he and his team are building on a large scale in London.

shca's client at Winchester House was Wates City of London Properties plc. The first scheme for the site, approved in 1990 but put into limbo by the recession of the early 1990s, was, however, dropped after Wates secured Deutsche Bank (db) as tenant and co-developer in 1994 and the project was redesigned to meet db's accommodation requirements. Planning consent was given in October, 1995. (In the interim, Winchester House had, of course, been badly damaged by an ira bomb.) db had taken over Morgan Grenfell & Co Ltd, the merchant bank, inheriting its complex of offices at 23 Great Winchester Street which focus on a handsome 1920s Classical palazzo by Mewes & Davis. db's Global Corporates and Institutions Division moved into Winchester House in March. At the heart of its operations are three open-plan dealing floors, on the second, third and fourth floors, each of around 4600m2 and accommodating up to 650 dealers per floor, a dealing factory of a configuration which would not, in fact, be permitted in Germany but which is typical of London. Other floors contain cellular offices, conference rooms and executive suites. The interiors were given to Pringle Brandon (which also advised db on base building modifications) and contain a striking collection of modern art works - db prides itself on its record of patronage.

The context of the development includes a group of distinguished listed buildings - the former Morgan Grenfell hq itself, Carpenters' Hall, and Dance's church of All Hallows, London Wall - and adjacent conservation areas. The principle of a 'groundscraper' scheme was not in dispute, but the form and materials of the new building were the subject of lengthy discussions with planners. The City was also keen to see some retail units included in the scheme.

The 1960s Winchester House had one asset worth keeping - a vast underground car park with over 200 parking spaces. Without the need for costly new excavations, the architect had an area where much of the plant and it equipment servicing the building could be located, allowing optimum use of upper floors. (Only 41 parking spaces were permitted in the development.) The existing basement slab and retaining walls were incorporated into the scheme. Use of setbacks, a device developed by American architects earlier this century, minimises the impact of the ten-storey building on the street. From London Wall, it reads as four storeys of accommodation on a double-height base, curved to address the street line, with a group of square columns marking the entrance, which is aligned with the tower of All Hallows. On Great Winchester Street, the facade modelling is more complex, indented to form a series of separate blocks - Walker likens them to town houses - which reflect the finer grain of the side street. The 1960s building arrogantly treated Great Winchester Street as a service road, accessing the hefty ramp down to its underground garage. Its dignity has now been reasserted. Since db has retained the former Morgan Grenfell hq, a second lobby entrance has been added to connect, visually and practically, to the Mewes & Davis building opposite. The buildings are also linked by a bridge section which spans Great Winchester Street where it joins London Wall, increasing the size of the dealing floors. The City is rarely happy about buildings spanning streets, and some hard bargaining between it and the developer was needed.

'Concrete or steel?' - the debate has occurred on many City construction projects. At Winchester House, structural engineer Bunyan Meyer & Partners achieved long spans using a post-tensioned in-situ concrete frame. The latter approach was well suited to the form of the building and the chosen cladding technique. One of the characteristics of the new City buildings of the 1980s, which took their cue from American fast-track construction, was the use of integrated cladding panels applied directly to the frame - by this means, a metallic 'modern' look or a more solid Post-Modern style can be applied at will. shca's approach at Winchester House was to apply natural limestone to a backing of precast reinforced concrete. The French stone was a good choice, with a warm texture, though planners were initially keen on Portland stone. Specially made windows are structurally glazed and set in regular openings which give the building a deceptively solid look - the bands of glazing on the corners to Old Broad Street and use of continuous glazing at the top of the building adds to its transparency. The City's insistence on some shops has also provided additional interest at street level.

shca is rightly proud of the partly double-height reception area which doglegs through the ground floor from London Wall to Great Winchester Street. Developed in collaboration with Pringle Brandon, which was heavily involved in the art work, lighting and tenant modifications, the reception provides a well-proportioned, carefully detailed setting for some imposing examples of corporate art - including a vast canvas by James Rosenquist and a large stainless-steel sculpture by Anish Kapoor as well as an enigmatic piece by Rachel Whiteread. In the us, this lobby would be open to the public. In London, it is private space, yet it has an American generosity.

Like his compatriots working in firms like som, hok and kpf - all those anonymous initials - David Walker is desperate to see the end of the typecast image of the American architect working in London. 'You can actually achieve results here which you'd never get, for example, in New York,' he says. 'In the us, the diagram is all. Here, you can get people to care about detail and finishes.' It is significant that one of Walker's teachers at Yale was Aldo Rossi - the influence of Rationalism at Winchester House is clearly discernible. After college, Walker worked for som, regretting the firm's drift into Post-Modernism. Walker is pleased that PoMo is dead. His aim is to create a modern, streetwise commercial architecture. At Winchester House, he and his team have succeeded in shoehorning a very big building into the heart of the City painlessly and with style. As the City ponders the prospect of a new generation of tall buildings, this skilful manifestation of an alternative approach commands study.

Structure

The original 1960s buildings on the site comprised a 22-storey tower over approximately 25 per cent of the site area, supported by high-density piling and five-storey podium structures on traditional pad footings. Existing basement structures varied from three to five storeys deep.

The density of the original piling under the tower precluded the use of a traditional piled substructure. Similarly, a simple raft would exhibit unacceptable differential settlements. A mathematical model was developed to reflect the varying stiffnesses of the underlying clay and existing piling. Future settlements were predicted and the clay was stiffened where required by additional small diameter piles. Thus a piled raft solution was adopted.

The client brief imposed requirements for column-free space; absolute adherence to the right-to-light envelope; maximum floor-to-ceiling heights within dealing areas and office accommodation, and incorporation of construction over a highway.

The floorplate geometry determined that the slabs would span between 12 and 14.5m and that the ninth, eighth and seventh floors would cascade to be supported by the sixth-floor slab.

Various structural alternatives were reviewed and the steel versus concrete debate was held. Consideration was given to an integrated zone for structure and services. However, this was considered to compromise future flexibility, and clear structural and service zones were preferred.

A prestressed post-tensioned in-situ concrete solution was developed with the structural zone limited to 425mm and this was adhered to generally, even on the transfer decks. Trough formers were incorporated to minimise the dead load yet maintain the eccentricity for the stressing tendons. Future-proofing the structure was achieved by incorporating soft zones for possible inter-floor staircases, as well as an allowance for future service holes to be cut through the topping between the slab ribs.

The foundation solution was both efficient and economical and proved to be a practical solution to the re-use of existing sites which have been previously piled. The superstructure had all the advantages of in- situ concrete in accommodating the flowing lines of the external elevation as well as providing a simple back-up face to receive the stone cladding. The post-tensioning achieved the clear long-span structures within specified structural depth and, with single-stage stressing being specified, permitted early formwork recycling.

Bunyan Meyer & Partners

cost analysis

SUBSTRUCTURE

FOUNDATIONS/SLABS £114.59/m2

Piled foundations, concrete raft, waterproof lining to existing basement retaining walls, basement suspended and ground floor slabs

SUPERSTRUCTURE

FRAMES AND UPPER FLOORS £96.34/m2

In-situ reinforced concrete frame with prestressed, post-tensioned upper floors and roof

ROOF £10.26/m2

Proprietary liquid-applied tanking membrane

STAIRCASES £11.09/m2

Precast concrete, mild-steel painted balustrade with stainless-steel handrail

EXTERNAL WALLS, WINDOWS AND DOORS £203.20/m2

Limestone cladding with granite plinth, double-glazed window with anodised aluminium frames

INTERNAL WALLS AND PARTITIONS £10.67/m2

Internal walls generally. Blockwork walling

INTERNAL DOORS £26.23/m2

Metal doors generally, timber-veneered wc cubicle doors

INTERNAL FINISHES

WALL FINISHES £20.93/m2

Limestone and marble to receptions, glazed panelling and polished plaster to lift lobbies, marble and timber panelling to wcs, painted plasterboard to circulation areas, painted plant rooms

FLOOR FINISHES £17.89/m2

Granite to reception and lift lobbies, agglomerate marble tile to wcs, screed to circulation areas (carpet by tenant), screeded plant room

CEILING FINISHES £6.38/m2

Plasterboard painted with feature bulkheads

FITTINGS

FITTINGS £18.58/m2

Signage, marble vanity units, sanitary appliances, facade access equipment, car-park barriers

SERVICES

DISPOSAL INSTALLATIONS £5.85/m2

Rainwater and condensate drainage

WATER INSTALLATIONS £3.75/m2

Pressured water system

SPACE HEATING/AIR TREATMENT £148.53/m2

Chillers, ahus, boilers, supply and extract primary distribution

PUBLIC HEALTH £7.19/m2

Foul water and car-park drainage

FIRE PROTECTION £16.14/m2

Sprinklers, dry risers and hosereels, detection and alarm

ELECTRICAL SERVICES £52.05/m2

hv supply, lv distribution, lighting, small power, earthing , bonding and lightning protection

COMMUNICATIONS /SECURITY £2.67/m2

Communications, cctv and security containment systems

LIFT INSTALLATION £47.86/m2

Seventeen lifts comprising eight passengers, five fire-fighting and four goods

STATUTORY AUTHORITY CONNECTIONS £8.15/m2

BUILDER'S WORK IN CONNECTION £24.45/m2

bwic, fire-stopping services installation

DEMOLITIONS

DEMOLITIONS £2,860,000

Phased soft stripping and demolition (including the provision of temporary service facilities for progressive tenant decant)

EXTERNAL WORKS

LANDSCAPING £6.00/m2

Roadway realignment and landscaping

cost summary

Cost per m2 Per cent

(£) of total

SUBSTRUCTURE 114.59 11.13

SUPERSTRUCTURE

Frame and upper floors 96.34 9.35

Roof 10.26 1.00

Staircases 11.09 1.08

External walls and windows 203.20 19.74

Internal walls and partitions 10.67 1.04

Internal doors 26.23 2.55

GROUP ELEMENT TOTAL 357.79 34.76

INTERNAL FINISHES

Wall finishes 20.93 2.03

Floor finishes 17.89 1.74

Ceiling finishes 6.38 0.62

GROUP ELEMENT TOTAL 45.20 4.43

FITTINGS 18.58 1.80

SERVICES

Disposal installations 5.85 0.57

Water installations 3.75 0.36

Space heating and air treatment 148.53 14.42

Public health 7.19 0.70

Fire protection 16.14 1.57

Electrical services 52.05 5.06

Communications and security 2.67 0.26

Lift installation 47.86 4.65

Statutory authority connections 8.15 0.79

Builder's work in connection 24.45 2.37

GROUP ELEMENT TOTAL 316.64 30.75

PRELIMINARIES 176.83 17.17 TOTAL 1029.63 100.00

EXTERNAL WORKS £288,400

Costs per m2 based on an external gross area of 48,070m2

Shell and core costs only, no allowance for category A works

Figures include an allowance of £1.2 million for tenant enhancements.

CREDITS

CONTRACT TYPE

Superstructure JCT 81, Substructure JCT 80

START DATE

September 1995

CONSTRUCTION PERIOD

September 1995 - October 1998

TOTAL FLOOR AREA

48,000m2 gross, 29,000m2 net

CO-DEVELOPERS

Wates City of London Properties plc, Morgan Grenfell & Co. Ltd

ARCHITECT

Swanke Hayden Connell International: David Walker, Michael King, Ray Pinches, Charles Quayle, Tony Barker, David Davison, Jim Ball, Dejan Dordevic, Melanie Freedman, Alejandro Gareri, Carl Grannell, Randall Heinrich, Sandra Hoskins, Brian Lacey, John Morgan, Nicola Murphy, Frank Nelson, Declan Nevin, Rachel Poulson, Neil Skilling

STRUCTURAL ENGINEER

Bunyan Meyer & Partners

SERVICES

M&E Design Services (Holdings)

QUANTITY SURVEYOR

John Shreeves & Partners

PROJECT MANAGER/CDM

John Shreeves & Partners

CLADDING CONSULTANT

Emmer Pfenninger Partner AG

FACADE ACCESS

Lerch Bates & Associates

ACOUSTICS

Hann Tucker & Associates

RIGHTS OF LIGHT

Schatunowski Brooks Associates

FIT-OUT

CLIENT

Deutsche Bank AG London

ARCHITECT

Pringle Brandon Architects: Chris Brandon, Paul Chapman, Colin Gow, John Pittaway, Helen Berresford, Jan Brandon, Isabel Cartwright, Peter Dobson, Alison Anslow, Kevin Burrell, Michael Evans, Jackie Ferguson, Richard Finnemore, David Freeman, Stuart Gilman, John Gouldsmith, David Kiernan, Peter Lill, Jim Losamore, Matthew Packham, Michael Rawlings, Lee Sims, Lee Ton, Sarah Wiggans, Anna Yau

STRUCTURAL ENGINEER

Bunyan Meyer & Partners

SERVICES

Cundall Johnson & Partners

QUANTITY SURVEYOR

Gardiner & Theobald

PROJECT MANAGEMENT

PA Consulting

CONTRACTORS:

SUPERSTRUCTURE

Hochtief/Costain Joint Venture

SUBSTRUCTURE

John Mowlem Construction plc

FIT-OUT

Interior plc

BRIDGE SOFFIT WORKS

Blenheim House Construction Ltd

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