An additional 16% of gross floor area has been added by extending three metres into an enclosed rear courtyard and the addition of a new top floor, which is designed to have minimal impact on the viewing corridoor and the historic facades. Completed in 1926 as the headquarters of tinned soup company Crosse & Blackwell, the challenge for maximising space in the building, though not listed itself, its situation in the Soho Conservation Area, with height restrictions imposed by the Strategic View Corridor from Parliament Hill to the Palace of Westminster. While an extension to the rear and the rationalisation of floor plates was relatively simple, the addition of the new top floor had to respond to Westminster’s many planning and rights of light issues. The lightweight structure of steel roof beams with a span of 12m provides a column-free space with the roof and glazed façades supported at the perimeter by wide solid steel ‘mullions’.
The rationalisation of the roof geometry and structure saved time and cost and reduced the complexity of the works. With the consent of Westminster City Council the new top floor extends slightly into the viewing corridor, as the impact on the conservation area was alleviated by inclining the window wall. Issues with the extension into the internal courtyard were avoided by angling the perimeter wall and setting back the extension above the third floor, angling the perimeter wall at fifth floor level to match the inclination of the new mansard window wall directly overhead.
The façade is refurbished to optimise daylight access and improve the glazing performance. At the base of the building the glazing was rationalised and replaced with frameless glass shopfronts. Internally the existing helical staircase has been faithfully extended and restored to provide a link to all the floors. Smooth dry-lined ceilings are suspended to house recessed luminaries and air grilles. The entrance lobby has a Travertine floor and purpose designed reception desk covered with red leather, a contemporary yet sympathetic response to the original building. Soho Square was completed in 2002.