At the cutting edge
High-bay warehouses are a well-understood building type. Indeed, they form that part of the built landscape which is seldom looked at or considered - edited out of our vision so much that we are somehow surprised when, like barbed wire fences, they pop up in the middle distance of photographs. For many people they do not constitute 'architecture' at all although, of course, they still have to get through the planning process.
But when a warehouse is not merely a distribution centre but also represents the core of a company's operations, much more complex decisions have to be made. This was what happened when architect Scott Brownrigg & Turner and engineer Price & Myers were appointed to design a new headquarters for Computacenter.
The company, which provides pre-configured computers for industry, has grown rapidly. It was previously on a number of sites but decided to centralise at Hatfield Business Park. Since the business consists of bringing in lots of computers, loading software onto them, and sending them out again, it needed substantial warehousing.
But, in addition, it needed to house headoffice staff and provide visitor facilities. This is important for Computacenter, which often brings in large parties of clients to show them how the company operates.
A welcoming environment The result was a set of three buildings: a large warehouse; a smaller office building, which is very much the public face of the project; and, smallest of all, a conference/ amenities building with a restaurant on the ground floor and seminar facilities above.
Visitors go there for an explanation of the company's operation, before seeing the warehouse and office operations.
'Computacenter was specific about its requirements, ' says Darren Comber of Scott Brownrigg & Turner. These were largely technical requirements for the warehouse, but for the office it wanted 'a cool, crisp environment, not overly opulent. There should be a calm face to the buildings, and an environment which would draw people to want to work there.' Part of the ethos was to bring together people who work in the warehouse and people who work in the office - previously on different sites - and allow them to share common facilities.
The office is in a splayed H form with a transparent atrium at the centre. It has a flatprofiled, steel-decked roof, supported on standard cold-formed zed purlins, which span between exposed steel trusses.
Jonathan Darnell of Price & Myers says: 'These take the appearance of having been formed from large slabs of stainless steel, with voids punched out of them to make the truss shape. In reality, they are fairly simple structural steel rectangular hollow-section tubes welded conventionally, but with additional curved sections of plate welded into the nodes to create the impression of punched voids.' Hidden cross bracing connected to the adjacent office roof structures restrains the column heads.
Exposed reinforced-concrete columns support the roof and a projecting glass entrance canopy. The primary structure for this also comprises stainless-steel roof trusses, in this case punched from flat stainlesssteel plate.
Although structurally the atrium is quite simple, Comber says: 'We paid a lot of attention to getting something that was quite sculptural. We spent time on the connections and on how it comes together.' Conceptually, it was important that the atrium was as transparent as possible, and did not have revolving doors. 'I hate revolving doors. As architects we always get trapped with tubes in them, ' he says. Instead, there are sliding doors. The need to avoid cold air currents was a determining factor in the size of the atrium. By making it a 4.5m cube, one door should have shut as the visitor passes through, before the other opens.
The drama of the atrium is increased by the presence of three steel-framed panoramic lifts. These are contained within one transparent core. Access to the four floors of offices is then across metal bridges. These bridges provide restraint to the glass fins supporting the glass walls and are linked to steel staircases without the need for intermediate landings.
Darnell has written: 'The steel bridges were initially conceived as being open threedimensional lattice trusses supporting a steel deck, but quickly evolved to become a number of universal beams spanning across the width of the atrium, but designed compositely with the concrete deck to reduce their bulk. They take some intermediate support from the columns forming the lift shaft and also have to span horizontally where they provide restraint to the glazing fins. The bridges are supported on sliding greased steel bearings on the office slabs to allow for differential horizontal movement between the concrete frame and the steelwork. As well as normal building movements, additional consideration had to be given to the likely elongation of the bridges because they acted as plenums, with warm air being blown around the steelwork, flowing through grilles to heat the space.'
If the atrium is the showpiece of the whole development, then the warehouse is, by definition, the most utilitarian. It has 22,500 m 2of distribution space in an 18m high building with three 'legs'. This configuration both reflects the functions that take place inside the warehouse, and allows room for future expansion. Darnell says: 'The building is designed around the block diagram of the process.' Structurally it is fairly conventional - designed as an economic arrangement of trusses and columns.
The building also incorporates two mezzanine floors for the workers who load the computer software. Located at the front of the building, these working spaces have necessitated a facade with windows. The arrangement of the windows has been carefully considered as part of the face that the building presents. Indeed, the whole ethos has been to avoid the impression of a looming, faceless, monolithic structure.
To this end, the architect originally designed the warehouse with a curved roof, but this was lost in a round of cost cutting - an economy which, Comber believes, the client now regrets.
The cladding was designed to diminish the apparent bulk of the building. There is a Sto render at the base, with the cladding stepping out above it. A range of aluminium profiled cladding was used in shades of silver and grey, with the largest profiles lower down. The effect is that the top of the building somehow fades away, fooling the eye that it is smaller than it actually is.
This diminution is the only aspect of the project to try to make less of the development than is actually there. Overall, the design team has aimed, successfully, to create something that is much more than just a faceless shed with a bit of office attached.
This is a development that is welcoming and has some personality, without any overtones of either elitism or opulence. It is a fitting project for a company whose business is rooted firmly in the twenty-first century.
ARCHITECT Scott Brownrigg & Turner
STRUCTURAL ENGINEER Price & Myers
PROJECT MANAGER Howard Associates
QUANTITY SURVEYOR AYH Partnership
STEEL CONTRACTOR Rohan Structures