For all its pragmatism, John Robertson Architects’ 199 Bishopsgate retrofit has a measured finesse, says Felix Mara. Photography by Richard Leeney
From the architect’s point of view, the most satisfying retrofits are those which offer opportunities to rethink and refine a project, as if standing on the shoulders of the original designer. In its retrofit of 199 Bishopsgate on London’s Broadgate estate, Cat B fitout-ready since September, John Robertson Architects (JRA) compounded its expertise in commercial office design with that of SOM, which designed the original building, completed 23 years earlier. And the practice has combined a sympathetic regard for the American multidisciplinary’s work with a critical eye. The project team rifled through options for the site, including a hotel. New-build offices were not deemed a strong contender because Hackney Council required proposals to fit within the existing development envelope: the game would scarcely have been worth the candle.
Having thus made savings on demolition and construction costs, as well as CO₂ emissions, JRA might have been tempted to propose blowing a hefty share of the budget on a new barcode rainscreen or spider-fixed glass wall. This cosmetic surgery, or more extreme measures, would be justified in the case of SOM’s horrific riverboat PoMo 135, 155 and 175 Bishopsgate to the south. But 199 is more palatable and, despite the tedious fenestration, less dated, though outclassed by the gutsy engineering of SOM’s Exchange House and Broadgate Tower (AJ 19.03.09) nearby. Also, the original curtain wall and cladding passed its MOT, meeting today’s permeability standards. The glazing, however, was replaced because it was at the end of its warranty period and a swanky new glass wall was added at ground and first floor level.
Though dating from an era whose office design approach has been dismissed as marble reception-making, the original building wasn’t fun to enter. Working up the architecturally problematic option of a corner entrance, on a curved facade, SOM designed a comparatively small single-story lobby with weak plan geometry. It was also too close to a nearby pedestrian crossing. At the expense of lost office space, the new reception is double-height, with much larger plan form, a sense of procession and a more frontal approach from Bishopsgate, addressing a wide, backlit onyx reception desk and back wall with polished stainless steel framing, inspired by SOM’s 1963 Beinecke Rare Book Library at Yale University, designed by Gordon Bunshaft. Turning towards the entrance barriers, you cross a honed, polished, light travertine floor under a Barrisol illuminated ceiling.
Lettable area sacrificed for the sake of the grander reception was reclaimed on upper floors by removing air-handling plant located on each storey. The original VAV system has been replaced by new centralised air-handling plant at roof level and space freed up in the basement is now used for bike and recyclable waste storage. Following changes in fire regulation standards from BS5588 to BS9999, it was possible to remove a fire-fighting lift to create more space. A replacement goods lift was also installed, potentially upgradable as a passenger lift with capacity for occupation levels of up to 1:8. These reduced core areas allow more layout options, ranging from legal offices with single-occupant rooms to open-plan corporate floorplates.
Having clawed back this lettable area, JRA then boldly sacrificed it by removing the top-floor mezzanine, creating prime double-height space with 345mm raised floors in an area which previously had low headroom, so there is an overall lettable area loss of 200m². ‘We’re competing with cheap lets at Heron Tower,’ explains JRA director John Robertson.
Clients British Land and Blackstone’s sustainable development policy, which underpinned the decision not to rebuild, required a BREEAM Excellent rating, in line with all new development and major refurbishments at the Broadgate estate since 2005. It also has an EPC rating of B. 199 Bishopsgate’s environmental performance is well documented online by AJ Sustainability editor Hattie Hartman and technical reporter Laura Mark, but two points are of particular interest.
First, with the facade’s upgraded U-values, the ventilation plant has to work extra hard to tackle overheating. Building services engineer Chapman Bathurst anticipated this using computer modelling, and high-performance glass was specified for the top two floors.
Second, because the development is built over Liverpool Street Station, ground source heat pumps were not feasible. Nor were solar or PV panels, given the restricted rooftop locations. In fact, no energy from renewable sources is generated onsite, but the GLA did not object, because 199 Bishopsgate is so energy-efficient, especially in its lighting and cooling design.
This building, winner of this year’s AJ100 Value Excellence Award, is one that cannot be ridiculed by entering by the back door. Every angle, including the views of the new roof, has been considered. It’s hyper-pragmatic, but delivered with extraordinary finesse. The building’s 199bishopsgate.com website doesn’t even mention that it’s a retrofit. As JRA director Fergus Moffat says: ‘Effectively, it’s a new building.