This six-storey steel frame development is located in a central London conservation area. The idea was to improve the building's potential as a commercial site while observing local authority building guidelines — the 19th century sections of the masonry façade remain intact.
Complex ground conditions determined the substructure design. The site sits on top of three London Underground tunnels. The planned Crossrail development connecting various underground rail lines across the city will see two tunnels bored 10.5m underneath the site. It is likely to cause subsurface and surface ground movements. In addition, clay and river terrace deposits are responsible for a heightened water table.
Our geotechnical team's solution was to turn the single storey basement into a concrete cassette raft by locking together the ground floor and basement. The cassette consists of 350mm thick reinforced concrete spine walls connecting a 750mm thick basement slab to a 400mm thick ground floor slab.
Internally, a glazed atrium rises through the centre of the building. Where possible columns have been positioned behind the façade to allow for an open plan office environment.