How Woods Bagot will change 10 Trinity Square with a glass ‘whirlpool’. By Kaye Alexander
One of the most iconic buildings in the City of London is to be reborn as a hotel and residential complex for highflyers in the financial services sector. Woods Bagot’s scheme for 10 Trinity Square, nicknamed ‘the whirlpool’ after the glass canopy at its centre, was granted planning approval by the City of London Corporation in May.
Woods Bagot has been working on the plans since 2006 when US property company Thomas Enterprises acquired the Grade II*-listed building to develop as a 121-bedroom luxury hotel and spa and 30 apartments. Previous tenant Willis Insurance vacated last year.
10 Trinity Square was commissioned by the Port of London Authority in 1911 through an architectural competition won by Edwin Cooper. Completion of Cooper’s Beaux Arts design was delayed by the First World War (it was finished in 1922) and its central grand rotunda – a 30m-wide reinforced concrete construction – was bombed in the Second World War.
Woods Bagot’s proposal reinstates this central focal point in the form of a glazed canopy that creates a circular central well. This requires the demolition of a nine-storey pentagonal extension added by Mills Group Partnership in 1976.
Woods Bagot worked with English Heritage to preserve as much of the building’s existing fabric as possible. A document drawn up in conjunction with heritage consultant Donald Insall Associates identifies a number of key areas of special interest.
The canopy allows vertical risers and other structural elements to be contained in the new-build areas, so much of the original fabric remains untouched. The main weight of the new roof, which projects out to rest on the existing building, is transferred down within the new build.
Building services are located in the basement and, by placing the service cores at the corners of the proposed courtyard, new, intrusive vertical elements, such as the lift shafts, avoid the existing building.
The three-year construction period starts with one year of ground works. In Buro Happold’s construction sequence, two tunnels will be dug below the west wing to create a route for the construction of the new courtyard basement and structure. The tunnels will also serve as permanent access and service routing between the basements. For the tunnels, a line of structural columns below ground-level will be removed and the lower ground-floor slab lowered to level one of a two-level basement.
No start date has been set, but completion is planned for 2012.
Two new floors, levels six and seven, are being created on top of the existing double-mansard roof. Access is through lifts in the extended cornerstone towers and servicing is in corner plant rooms, indicated in the glazed radial roof plan by grills.
The roof drops down at an incline into the central courtyard, and the radial geometry is accentuated by the vertical fins that begin at the edge of the roof and turn down. Building maintenance units will run on a track that is at the junction of the glazed roof and the beginning of the fin detail.
The lower section of the courtyard is covered by a glazed dome, which is supported by a ring beam and inclined vertical structure, standing proud of the facade at first and second-floor level. First-floor hotel room balconies will overlook the rotunda lobby.
AREAS OF SPECIAL INTEREST
Woods Bagot will conserve many of the original interior features while incorporating the servicing requirements of a modern hotel. As such, plaster ceilings, such as those situated in the south wing of the second floor, are being maintained and the original air vents may be used in the new HVAC strategy.
Throughout the second floor rooms in the south and west wings, existing fan-coil heating units, housed in awkward panelled containers under the windows, will be replaced with versions that sit flush with the adjacent panelling to allow for curtains to be closed.
This level of detail has been followed through into the corridors, where plumbing waste and vent pipes are contained by extending existing pilasters to allow pipework to travel vertically in the void formed behind.