Despite different contractors working at different times on different bits of the same building, Foster and Partners' Ken Shuttleworth's team stayed cool during design and delivery of the social sciences centre for Oxford University. They built full-size mock-ups, and even then weren't too proud to tweak the specification the second time around.
Project director Max Neal talks to Sutherland Lyall In the mid-1990s, Oxford University ran a beauty competition among half a dozen practices to find the designer for a new social sciences centre. Built just across the canal from St Catherine's College, it is next door to Leslie Martin's St Cross building. As its full name, the Centre for Advanced Studies in the Social Sciences, faintly suggests, this is an omnibus postgraduate centre. Socially orientated subjects such as economics, criminology and politics mingle under one roof, the manifestation of an intention to encourage interaction between people with specialist subjects and the formation of new interest groupings. The basic physical elements are a library, lecture theatres, work spaces for graduate students and staff offices.
Shuttleworth's team designed the whole scheme as a single entity, but it had to be built in two phases. The first of these was a smaller three-storey block which contained offices, some library space and a grand, almost ceremonial staircase whose scale makes sense only now that the second block has been added.
This is a rather larger block whose structure is now just about watertight and ready for the separate fit-out contract. Subcontract tenders have just been opened.
The ground floor of the combined phases is occupied almost entirely by library stacks, seating and a zone of group study rooms across the north wall. The remaining two storeys of the first block and three storeys of the new block are given over to staff rooms, mostly around the perimeter, and graduate study spaces. These are in open-plan arrays wrapped around the central atrium, which contains stairs and has lecture and seminar rooms to the east and west, the new block having a central atrium.
Neal explains the design: 'This is more akin to an office building with efficient large floor plates and an atrium in the middle pulling light into the office spaces. It is also the major circulation zone, with lecture theatres opening straight on to the atrium. The aim was that the second building should be visually contiguous with phase one (we did the competition design at the end of 1995) and by and large we have replicated what we had there.'
The in situ reinforced concrete frame is on a 5.4 x 5.4m planning grid. This is unusual for an office building but the driving force for this grid was based around the book stack spacing - and it worked reasonably well with the 2.7m wide cellular offices. The 5.4m grid is expressed outside the building, with a structural frame of 5.4 x 3.5m. The structural elements are 400mm wide, and are faced with precast concrete panels of the same face dimensions.
Pragmatic about contracts The university surveyors' office is anxious to get value for money and deploys whatever contractual arrangements will achieve that aim. So the first phase was built under a management contract with Heery, in which Foster had the normal architectural role in the design team - and was lead consultant. For the second phase, the university decided on a JCT design-build contract with HGB Construction as main contractor and with Mace appointed as the project manager, to which quantity surveyor Turner and Townsend is the consultant. Here Foster carried out the full architectural role up to tender stage and was then retained by the university, as Max Neal explains, 'to make sure that what is built is in accordance with the tender documentation. At the same time we were separately appointed by HGB to act as architects for themselves to develop the designs with their subcontractors and do the documentation. So we wear two hats: one as HGB's architect and the other as the executive architect to the university.'
There doesn't seem to be a conflict of interest here. Neal points out: 'We manage the project as virtually (and contractually) two separate teams. There are advantages with this because we can find out what the HGB team is doing and, should it be necessary, can nip things we're not happy with in the bud.
'We have always worked with the subcontractors on the tender documents, ' he continues. 'What we do on all jobs is to prepare design intent drawings rather than detailing everything down to the last bolt. So we know what we want without necessarily giving the exact thickness of profiles. On a piece of cladding, we would show the outside of the profile without showing the exact detail of what only the subcontractor can do himself.
And we have quite prescriptive specifications of the performance. It's the way we have tended to work from the early days - it's about working with industry.'
On the issue of picking specialist subcontractors' brains and then putting them on the tender list along with all the rest, Neal takes the view that 'in competitive tendering you rarely have the luxury of working with one subcontractor - they have to tender'.
'We get them in and get them to understand what and how they might go about carrying out the job or what kind of product they might propose, ' he continues. 'But in terms of the amount of work they actually do, it isn't onerous, but it enables us to draw up something that is realistic - which can be reproduced because it is informed by industry. Say on cladding, what might happen would be that we would talk to the cladding contractor. They might bring in an expert from the manufacturer supplying the profiles and, of course, we prefer to talk to the technical people rather than marketing people.'
Specify with Fosterspec Most medium and small practices now use NBS but the Foster office, probably since Stansted Airport, has used its own specification, Fosterspec. Neal says: 'It is used on all our projects around the world. So if we are doing a French project it is adapted for any peculiarities of French construction. It was written for us by Schumann Smith, now part of Davis Langdon & Everest, and is modified by experience and changing regulations and standards.'
The Foster office runs CAD now on PCs and has always used MicroStation. Neal is aware that a lot of the industry uses AutoCAD, but MicroStation can read its file structure.
The translation is never totally consistent and, Neal says: 'This project isn't like the GLA building whose complex geometry meant data had to be issued in terms of coordinates to avoid any 3D errors. Oxford is a straightforward building.' And so it has proved.
Working it out Neal says: 'Our standard working method is that full-size mock-ups are built on site. We comment on detailing and workmanship and the testing is done by Taywoods at Leighton Buzzard. It's normal to do a lot of prototyping and it is all part of the tender. The cost is rarely an issue. On, say, a frame, the cost is relatively negligible. It stops unpleasant surprises and it has to make financial sense to make sure the system is watertight. It also gives a visual benchmark for the client. We encourage the client and their safety officers to look at the elements so they actually sign them off or come up with comments. With health and safety a new and important part of life, we always strive to get the clients' safety people in as active members of the team to sign off the stages just as we do the building control officer.'
Matching up One of the changes between phases was the treatment of the exposed in situ concrete, which in the first phase was a micro-silica top mix left as struck. Neal explains: 'For phase two (for which the contractor was Hertfordshire firm Getjar) we did a number of valueengineering exercises and ended up using a medium-grade concrete. When the formwork was struck we then had a Keim Concrete Lasur translucent paint applied. This enables us to use a far cheaper concrete mix and, at the end of the day, to get the same visual result.'
Another change was in the cladding. On phase one it was a stick and panel system with aluminium extrusions built by Harty Holdings. On the current phase this was changed to a unitised aluminium system from M Price, using extrusions made by Reynaers. Neal says:
'When we met Price to develop the design, Reynaers people were normally present.'
The precast-concrete facing panels for both phases were by Sterling Services, although the details were different as one system is stick and the other unitised. The glass for both was from the German firm Okalux.
The clear glass is low-iron double-laminated with a high-performance sun-control coating. The translucent glass is low-iron doublelaminated with a white PVB interlayer between the laminate sheets either side of the cavity. The cavity is filled with a capillary honeycomb structure with glassfibre tissue layers either side.
This is an air-conditioned building, which can also deploy natural ventilation along the perimeter. There is a seemingly random pattern of clear and translucent glazing on all facades except the east one. On phase one there are top-hung windows in the clear panels. On phase two, the pattern is tripartite:
there are clear panels, translucent panels and solid aluminium-clad full-height pop-out panels. They have a handle on either side and a scissor mechanism, which means that, when they are open, instead of sloping they remain vertical. Because this means there is a larger area of free air, 100mm on all four sides, the opening panels themselves could be narrower.
Neal says: 'The world is going from straight desks to L-shaped desks and these narrower vents enable us to install them. So every cellular office has one pop-out vent, which is especially useful in spring and autumn.
They were made by M Price as part of the curtain-walling contract. It was something we devised using standard components (the scissor mechanism is used in rooflights), put together in an unusual way.' Inboard of the cladding are big sliding blinds - stretch fabric on a frame running in top and bottom tracks, which parks in front of the translucent panel.
Where the earlier phase had a pattern of translucent and clear, here there is a pattern of one clear, one translucent and one 380mmwide aluminium pop-out panel. Although the elevations in the two phases are different, they are clearly in the same vocabulary.
The roof, by Hammersmith firm Rock Asphalte, is an inverted type, comprising reinforced hot-melt rubberised bitumen membrane applied to the structural concrete deck with interlinking polystyrene insulation, a lapped filter sheet and then stone and pebbles.
The low-pitched atrium roof, built on falsework above the roof slab by Robertson Roofing, is surfaced in Trocal. The concrete atrium roof is side-lit. Neal says: 'It produces a nice quality of light, is good for cleaning and maintenance - you don't have to replace glass three floors up - and it was cheaper than glass.'
Aluminium copings are by David Allgood - not the Allgood D Line people.
Lee Warren was the architectural metalwork contractor for the flat-bar metal handrails and the escape stairs. In phase one, the escape stairs were of in-situ reinforced concrete. In phase two, for cost reasons, they have metal-folded tray treads and risers, and welded stringers. The trays are filled with 50mmthick mesh-reinforced concrete. Renson metal louvres are used around plant rooms.
Principles to come Summing up the practice's position on merging the two phases visually, Neal says: 'The message is that we have kept to the same principles as in phase one, but where there were ways of saving money or saving the construction programme we have looked at alternatives. We have the same exposed frame and soffits in phase two, but because floors are open plan we are suspending acoustic absorption locally where it's required. We used it in the Greater London Authority building committee rooms - it is a solid-looking material, a sort of ribbed painted timber board.
'The other big change is that the first phase was carpeted and in the second we are looking at vinyl flooring - there are quite large openplan areas and we are keen to maximise the effect of light bouncing around. Carpet in a practical colour has to have a certain tone to it so a light colour wouldn't be practical. But with vinyl we can achieve quite a light colour.
The first-phase internal partitions were drylined with solid doors. On the current phase, walls between offices are a standard demountable partition system with double glazing and integral blinds so that from inside there is always an awareness of the sky beyond.'
CREDITS ARCHITECT Foster and Partners:
Ken Shuttleworth, Max Neal, Graham Longman, Daniel Poehner, Louis Lafargue QUANTITY SURVEYOR Turner and Townsend STRUCTURAL ENGINEER Andrew Kent and Stone SERVICES AND FIRE ENGINEER Roger Preston and Partners PROJECT MANAGER Mace ACOUSTIC ENGINEER Sandy Brown Associates FORM OF CONTRACT Design and Build GROSS EXTERNAL FLOOR AREA 10,182m 2TOTAL COST £22,033,525 inc VAT START ON SITE February 2003 COMPLETION ON SITE May 2004 CAD PACKAGE USED MicroStation SUBCONTRACTORS AND SUPPLIERS Curtain walling Reynaers; curtain walling subcontractor M Price; precast concrete cladding Sterling Services; asphalt roofing Rock Asphalte; single-ply roofing Trocal; single-ply roofing contractor Robertson Roofing;
architectural metalwork Lee Warren; lifts Kone; aluminium copings David Allgood; fairfaced concrete frame Getjar READER ENQUIRIES David Allgood 1600 Getjar 1601 Keim 1602 Lee Warren 1603 M Price 1604 Okalux 1605 Renson 1606 Reynaers 1607 Robertson Roofing 1608 Rock Asphalte 1609 Sterling Services 1610 Trocal 1611