The project involved the redevelopment of the north half of block W4 to provide retail space on the lower and first floors and office units above.
The new building retains the façade to both Regent Street, New Burlington Street and brick vaults dating from the 1800s which were previously used as wine cellars.
The Crown Estate
Exemplar
Allford Hall Monaghan Morris
The new steel structure was long span providing column free space from the core to the façade, with an integrated structure/services solution with bespoke holes in the beam webs.
The top floor office is provided with exposed bifurcated beams which provided a full height curved glazed façade giving magnificent views from this level.
The biggest challenge was retaining the existing brick vaults and building a second level basement adjacent. The vaults had to be restrained at all times to prevent the arch structures spreading. A complicated temporary works sequence of king post walls and secant walls were used to achieve these objectives.
A piled foundation was adopted due to the presence of the retained vaults not allowing a continuous plate of concrete to spread the loads.
One of the façades to New Burlington Street was dismantled and rebuilt in a stretched form allowing the floor levels behind to be similar to the main façade to Regent Street.
A mini atrium was provided behind a smaller façade to New Burlington Street as the new floors did not coincide with the existing façade. A frame work was provide behind the façade formed in box sections to minimise the depth, and support the thin brick structure.
The interface between the new and the old façade needed careful review and investigation.
3D modelling allowing integration of the services and structure to be co-ordinated prior to installation on site was adopted. The modelling allowed temporary works to be located to avoid clash with the new structure. A point cloud survey was carried out to map the installed temporary works as a further check post demolition.