The 13.5 ha site is being developed and marketed by Stanhope as an office that is so much fun to work in that staff will not want to work for another employer ever again. So, they will have on-site amenities such as a health club, cafés and restaurants, themed landscapes, open-air meeting places and an estate management office billed as "The Thoughtful Centre". This will have a remit of providing ad hoc surprises to the workforces in the 11 buildings that will eventually make up the development.
The park has been masterplanned by Richard Rogers Partnership as 11 office buildings ranged around a central lake, complete with cascading waterfall. However, the father of the project is Stanhope chief executive and architecture champion, Sir Stuart Lipton, who describes the Utopian campus as a "marriage of efficiency and quality of life".
If the marketing literature stresses the quality-of-life side of this equation, the buildings themselves are ruthlessly dedicated to efficiency. The need to wring every last square metre out of the floorplate has produced designs that do not have the "Rogers look", even if the emergency stairs have been pushed outside the building envelope. And the quality of life may be good, but you suspect that it will be enjoyed with a large number of other people.
Neale Brydon, project director for construction manager Bovis Lend Lease, had his own benchmark of efficiency when he saw the construction timescale. In contrast to the serene landscape planned for the offices, the build programme is far from relaxing. The first phase of the development includes three office buildings, the greater part of the site's landscaping and the looped perimeter access road – all to be completed in fewer than 44 weeks. "The quicker we build it, the quicker we can get our product to the market," says Simon Jenner, the Stanhope man overseeing the project.
The architect was the first member of the construction team to feel the pressure of the tight deadline. Richard Rogers Partnership was appointed in April 1999, four months before the planning application for the first three buildings and accompanying infrastructure modifications was submitted in August.
Once the planners had approved the scheme, the detailed design could begin. "That's when the gun went off and we had to start to work up the design with the contractors," says project architect Richard Paul. "We had just three months to produce the design information."
To meet the tight build programme and help simplify the construction process, Richard Rogers Partnership opted to use the same kit of components on all the buildings. On site, the first three offices – buildings one, two and three – are nearing completion. The result is that they look remarkably similar. In plan, they are all roughly square, set out on a nine-metre grid, and stand four storeys high, with out-of-sight car parking in an undercroft. They are supported on a precast concrete frame and have fully glazed elevations crowned at roof level by a projecting, horizontal lattice of angled louvres to shield the facades from the sun. Inside, all the offices have large, uninterrupted floor plates surrounding a core area housing WCs and lifts.
Paul is an old hand at designing business parks, having been involved in Stanhope's Stockley Park, near Heathrow, while working for Foster and Partners. However, he describes Stockley Park as "an architectural zoo", and claims that Chiswick Park will have much more cohesive architecture with "subtle differences between the buildings".
On the other hand, Paul reveals that Stanhope was very much in the driving seat as far as design went. He was, he says, "shackled in all directions" by Stanhope's specifications. "They were very prescriptive in what they wanted," he says, citing a "myopic tendency towards toilets" as an example: "Even the diameter of the washbasins was specified."
On site, the central core of structural steel was the first part of each building's superstructure to be constructed. In addition to housing lifts and WCs, the core also provides lateral stability to the structure. Working with concrete contractor O'Rourke, the team then developed a concrete frame for the buildings, using a grid of precast concrete supporting columns.
Brydon explains that precast was chosen to save time "by eliminating all work that involves casting concrete vertically". The columns are positioned on "capless" piles using a single locating dowel. "This saves a considerable amount of construction time, compared to using pile caps, which more than makes up for the minor cost increase of having to use a slightly thicker pile."
Precast concrete sections were also used for the floor-edge beams, as a "concrete necklace" around the 2200 m2 post-tensioned concrete floor-slabs, which were cast in two halves. "By using a post-tensioning system, we were able to finish each floor in just a week and a half," says Brydon.
The technique meant the floor slabs could be thinner, lowering the eventual height of the buildings by about 1.5 m. This saved money on cladding, and it meant that downstand beams were not needed to support the floors, so O'Rourke could use simple table-form shuttering to cast the slabs.
It was the cladding design that posed the biggest threat to the construction programme. A simple solution had to be found for the curtain wall. "We were given a tough cost target from Stanhope for the cladding," explains Paul. Stanhope's Jenner says £300/m2 was a tight but not insurmountable figure. Aside from cost and buildability issues, the architect also had to maximise the glazed area to allow natural light to flood the floor plates. "With the floors 18 m deep, we had to use as much glass as possible to allow light deep into the building," says Paul.
The architect decided to opt for repetition, specifying the same glazed panels for each wall irrespective of orientation, and choosing instead to add different shading configurations to the building's exterior.
Despite having gone to great lengths to ensure the panels were quick to assemble, the schedule was almost scuppered by a European shortage of coated glass. "The architects were so concerned over the delivering time, they drove to the factory and said 'we want our glass'," says Paul.
The curtain wall was assembled from 3.9 m high, three-metre wide units, delivered to site fully glazed. It took one week to install brackets for the cladding, and just six to seven minutes to winch each panel into place by crane. Cladding to all three buildings took less than five weeks. "In fact, the cladding was installed so fast, the supplier had trouble keeping up," says Jenner.
As Brydon agrees: "It would have taken up to three times longer to install a bespoke stick system and, of course, we'd have had to erect an external scaffold."
Inside, the philosophy used to define the buildings' elevations and method of construction has prevailed. The large, bright office floor plates have a clear floor-to-ceiling height of 3 m and feature a 300 mm ceiling void and a 400 mm raised access floor.
Building one is now almost complete. The final sections of the external escape stair that cuts diagonally across the glazed facade are being manoeuvred into position, ready for handover on 17 November. Tenants have signed up for buildings one and three, and negotiations are under way for building two.
In the next few weeks, work will begin on the second phase of the scheme, when piling for building 11 starts, followed by work on building 10 immediately after Christmas. "The programme is based on the order the buildings are let in, rather than on the order I'd like to construct them in," says Brydon. "But having completed the three buildings in phase one on time and to budget, we know phase two will be quicker."
developer Stanhope masterplanner and architect Richard Rogers Partnership landscape architect West 8 structural and services engineer Arup cost consultant Davis Langdon Everest construction manager Bovis Lend Lease piling O'Rourke Civil Engineering concrete frame O'Rourke Civil Engineering steel frame Westbury Tubular Structures brickwork/blockwork Lyons & Annot curtain walling Josef Gartner & Co UK external architectural metalwork Merlin roofing Prater Roofing dryline partitions R&S suspended ceilings Astec Projects raised floors Hewetson Access Floors marble/granite floors SCI Stone Cladding floor finishes Tyndale Carpets architectural handrails and metalwork Custom decoration Cosmopolitan Group WC fit-out Swift Horsman joinery and general fit-out Swift Horsman mechanical services Sulzer Infra (UK) electrical services T Clarke ductwork Gardner & Co operation and maintenance manuals Watson & Sole Associates commissioning Commtech building management system Eton Associates lifts Otis