Situated in midtown, on the eastern edge of the City of Westminster, the 44,000 sq ft island site of 48 Carey Street is surrounded by institutional buildings such as the Royal Courts of Justice, the Royal College of Surgeons and the London School of Economics. The existing seven-storey building was demolished to the basement slab and replaced with a new nine-storey residential building with a further basement level.

Key technical challenges

The building height is limited by planning considerations. To achieve a viable scheme at nine levels, the floor slabs (spanning up to 8.0m) are restricted to 200mm thick. Post-tensioning is used with careful integration of anchorages, façade fixings and thermal isolation hardware. The slabs also support stone-faced cladding in line with the surrounding buildings.

The building plan (80m x 60m) is arranged around a central courtyard, has no movement joints and uses a pour-strip approach to limit shrinkage stresses and relieve restraint from opposing cores during post-tensioning.

To simplify basement construction and minimize temporary works, the existing upper-basement walls are retained and the lower basement constructed using secant walls installed within the existing basement zone.

A raft slab is founded within the London clay and designed for residual differential heave pressure in addition to gravity loads.

RBG carried out analysis to determine the locked-in stresses and differential settlements for the proposed construction methodology and sequencing, which entailed the building being constructed in two halves.

Project Metrics

Project Value:
£80 million GBP
Year Completed:
Building Metrics:
148 apartments
9 storeys with double level basement

Project Metrics

PLP Architecture
Primary Contractor:
Robert Bird Group Services:
Structural Engineering
Civil Engineering

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