SSDA Awards
COMMENDATION – One Great Cumberland Place, London
Helping to protect the capital’s historic streetscape, a steel-framed office and retail development combines a retained façade with a new modern interior.
FACT FILE
Architect: Allford Hall Monaghan Morris
Structural engineer: AKT II
Steelwork contractor: Bourne Steel Ltd
Main contractor: Galliford Try
Client: The Portman Estate
Directly opposite the Marble Arch monument, a new ten-storey development, sitting behind a retained façade has significantly upgraded a building originally built in the 1920s.
The project involved retaining the existing façade from street level to up level six, while behind it a full demolition and a steel-framed rebuild took place. The work created three floors of retail space and above this a further seven floors of high quality Category A office space.
Commenting on the decision to retain the façades, which run along the main Marble Arch elevation and Great Cumberland Place – the other two sides, to the north and west of the building are party walls, project architect AHMM says the work ensures the restoration, protection and reinterpretation of the existing historic architectural features.
The top levels of the façade were removed during the demolition programme and have been replaced with new stone-clad elevations that match and complement the retained parts.
Once demolition was complete, a temporary retention system for the façade was installed and the existing basement enlarged into a two-level subterranean area.
Bourne Steel were then able to get the steelwork erection programme underway. Based around a regular column grid pattern of 6.5m x 9m and stabilised by a single concrete core, the steel frame supports metal decking with a concrete topping to create a composite flooring solution for the new building.
New steelwork connects to the retained façade’s steel columns via bolted connections and provides the support for the old structure.
“They are two separate structures; the steel frame is founded on new raft foundations, while the façade is on pad foundations. So, in order to negate against any differential movement, they are joined by a sliding connection,” says Galliford Try Senior Project Manager Barry Kingscote.
The majority of the structure’s steel beams are fabricated plate girders with bespoke cells to accommodate the building’s services within their depth.
“The soffits have been left exposed within the completed building, along with the steelwork,” explains Bourne Steel Project Manager Duncan Wyatt. “Consequently, we applied a decorative intumescent paint finish to the beams and columns at our fabrication workshop. This cut down onsite works, as we only had to repaint the connections and any knocks and scratches.”
The exposed interior of the office floors gives the building a modern and ‘industrial looking’ environment. Meanwhile, adding some irregularity to the new steel frame, there are set-backs on each of the floors that are above the retained façade. Transfer beams are located on floors six, seven and eight in order to support the irregularly-positioned columns that help create the three steps in the building.
In summary, the judges say this high-specification development, is part of the prestigious Portman Estate, so demanded a sensitive response to modernise a valued period building. Comprising retail and high quality office space, an efficient steel frame integrates a new ten-storey building within a retained 1920’s original façade, where new floors and openings have been sensitively designed to correspond with historic elevational details.