CAVENDISH PLACE
Location: London
Status: Tender
Architect: Squire & Partners
Client: Bridge Group
Introduction
15 to 19 Cavendish Place is a retrofit and extension- both vertical and lateral- of a late 1920’s structure, in the heart of Westminster. The building was acquired with an existing planning consent for a two storey vertical extension, working closely with Squire & Partners on massing studies we have managed to increase this to a three-storey extension, within the capacity of the existing six-storey structure and its foundations.
Limited record information was available from the original construction, but we knew that it was a purpose-built office with a ground floor showroom. Similar to much of the Regent Street Conservation area, the building was designed in the Beaux Arts style. A symmetrical and ordered composition, the building features a core at each side of the building. However, by noting the alignment change between ground and basement we were able to work out that the building was detailed as a sway frame and the cores are none load bearing.
Retaining the western core and its heritage staircase, enabled us to consolidate the vertical circulation into one side of the building, removing the eastern core an opening up the floor plates. By utilising the terraces as an external fire escape route we optimise the spatial configuration for the buildings new life.
Approach
To maximise the potential for this building a steel frame was essential. The lateral extension infills an old lightwell to the rear of the building, and as the escape switches sides, the terraces step in and a concealed bracing system helps to stabilise the structure which could only realistically be achieved in steel. Using a composite deck system to create a robust, fire-resistant solution, enabled the additional weight to be kept to manageable levels.
The introduction of a new concrete core to facilitate the new lift locations created an opportunity. As the existing structure had been designed using sway frames in the front and rear facades- to provide the east/ west stability system, it would require significant strenghtening to stability the additional extension floors. By utilising the new concrete core, the stress was removed from the original system and the structure could be extended without the need for strengthening.
