Sutherland Lyall talks to Sidell Gibson Architects about the unique diagonal atrium and frameless bays of its office in the City of London
Sidell Gibson Architects’ central London office building, next to the Central Criminal Court and round the corner from St Paul’s Cathedral, is set for completion in March. Its Old Bailey street facade is a Portland stone grid with slightly projecting glass bays.
Round the back, which faces on to Amen Court, the upper part of the elevation curves up and becomes the roof. Inside is a unique atrium: instead of being an orthogonal space, it curves up diagonally to the rear of the building and scoops light down into each floor. A basement floor accommodates some offices and is lit from the back of the building and the ground-floor stairwell.
Sidell Gibson partner Stuart Clements explains the planning stages of the project: ‘We have had the Old Bailey project on the books since the late 1990s. It was then a completely different scheme: we were going to retain the existing facade. [When the project was restarted] the City planners asked us if we would reconsider the design. They were against retaining the facade, and suggested to us that we could do something a little more radical.
They suggested we work in collaboration with another practice and a number of architects were mentioned, including Avery Associates Architects. We knew [practice director] Bryan Avery, so he was invited in. We were quite happy with a brand new building and Bryan came up with the current scheme, with projecting frameless bays down the Old Bailey facade, and the diagonal atrium. We followed the old sightlines [at the rear] so we got planning relatively easily.’ As part of planning, the back wall is covered with climbing and trailing plants.
The client, office developer MWB Business Exchange, decided that this should be a JCT design and build contract with the quantity surveying company, Matrix Consult, advising the developer directly on cost and fulfilling the role of project manager. Sidell Gibson and structural engineering firm Pell Frischmann were novated to the main contractor, Bowen. Mechanical and electrical company, Elementa Consulting, was retained as advisor because Bowen had its own services engineers. Although there were two principal contracts, one for demolition, the JCT was a one-stage design and build contract.
Work on subcontracts and details commenced as soon as Bowen was on board. The amount of time available for negotiation was enhanced by a hold-up of several months in the demolition programme: the proximity of the Old Bailey had made demolition tricky.
Bowen submitted a fixed-price lump sum bid and tendered on fairly complete information. Clements says: ‘We were appointed by MWB to do the initial design and we were retained almost all the way from Stage E to Stage F, so the tender information and the majority of design work had already been done.’
On the selection of Bowen, Clements says: ‘We interviewed the lowest three tenderers and although one of the funders had a [different] view, MWB decided to go with Bowen, partly because they had worked with the construction team on a previous project and they knew what they were getting. The usual scenario is to go with people you know.’
Clements continues: ‘There is an issue with design and build, because you have been working for the client and suddenly you are thrown to the [contractor’s] side. It is a difficult scenario. Sometimes the client asks us to do things, but we are contracted to the main contractor.’
Once the contract was novated, there was still a lot of work to be done with Bowen on the way the subcontracts should be packaged, and extracting the information needed for subcontract tenders.
The progress of the work was monitored via monthly meetings with every party involved in the building, including the client and funder, Standard Life. Design workshops chaired by Bowen took place for each package. Clements says: ‘Workshops are the best way of getting the issues solved. We have the drawings on the table, felt-tip pens out and the subcontractor says, “OK, we can do it this way”, and things get resolved.’
SPECIFYING AND FIXING
Project architect Russ Dent explains the specification method: ‘We used the electronic version of the National Building Specification (NBS). It’s easier to use than the printed version. Our contractor liked to use the “…or similar clause” but we had to be fairly strict [about materials] because we had to take on board what the planners wanted, and our choices had been signed off by the client. But we were flexible. For example, the planners said the stone cladding had to be Portland stone. We originally designed the stone cladding as a rain screen. But the contractor came up with the idea of attaching the stone to precast concrete panels, which was easier to fix on site.
‘The planners agreed to a reconstituted stone facing on precast concrete panels for the rear elevation, providing we put in a green wall.’ The other advantage for the contractor was that the thickness of the front elevation stone could be reduced from 75mm to 50mm. The precast spandrel panels were 7.5m long by around 1.5m deep with the two-storey facing panels measuring 7m long. They had built-in fixing eyes and were craned into position.
On selecting the glazing contractor, Dent says: ‘Initially we wanted the whole envelope to be done by one subcontractor. At that time, the market was very busy and we had difficulty getting glazing contractors to do this. In the end we went to a dozen glass >> people and Komfort Workspace came in and said they could do all the glazing. Most wanted to use glazing bars, but Komfort were known for being able to do frameless glazing. We developed the construction for the bay and atrium with them. We said “this is what we are trying to achieve and, if you can’t do it, what can we do?” And they came up with a solution which met our design intent.’
INTERIORS AND AMENITIES
The air-conditioning system is a four-pipe fan-coil system with a plant located in the small top floor and basement. Ceiling tiles are standard SAS perforated metal. The main interior finishes of note are found in the entrance area where floors are French limestone, slightly more hardwearing than Portland stone, by interiors specialist Granite and Marble Services. Dent says: ‘We have used them before, and this sort of thing is their bread and butter. They work very quickly and their quality standards are high. Bowen went out to the market with tenders and Granite and Marble prevailed anyway.’
Title of project 7-10 Old Bailey
Client MWB Business Exchange
Architect Sidell Gibson Architects with Avery Associates Architects
Main contractor Bowen
Quantity surveyor Matrix Consult
Structural engineer Pell Frischmann
Services engineer Elementa Consulting
Form of contract JCT 2005 Design and Build
Gross external floor area 9,360m2
Cost £22 million
Start on site September 2007
Completion on site March 2009
CAD package used AutoCAD
7-10 Old Bailey, London, by Sidell Gibson Architects with Avery Associates Architects