28 Dorset Square, London, United Kingdom

28 Dorset Square, a Georgian building near Regent's Park in London, was converted for office use in the 1960s, and a new concrete extension was added. The owner wanted to increase the rental value.

The practice's fundamental task was to emphasise the elegance of the Georgian building, and give the 1960s building an equally distinctive, but more refined appearance. The site required materials that would respond to the surrounding buildings: the brick and stucco of the Georgian terraces of Dorset Square, and the red brick and stone of Marylebone station. While respecting the context the client wanted the building to be distinctive in its own right, as well as contextual, and stand out as a contemporary intervention.

The buildings now command the highest rents in the square.

Dorset Square strategy

The strategy was, firstly, to carefully restore the Grade II-listed Georgian building's façades. Secondly, floor space in both buildings was released by creating a new full-height glazed link between them, with a common staircase and lift core, which meant that staircases in both buildings could be removed.

Thirdly, the external treatment of the 1960s building, in terms of surface and detail, was designed to repeat the Georgian building's key proportions and horizontal division. This was achieved by continuing the alignment and size of the Georgian window apertures, and by producing a Georgian podium with banded masonry on the ground-floor elevations.

In the Georgian segment, a new service zone was positioned to open up sight lines within the floors and give clear views into Dorset Square.

The practice considered demolishing the 1960s building but, on the grounds of sustainability and economy, stripped the structure back to its frame and reconstructed its shell. The building was reworked in Jura limestone, which featured in the conservation area. Frameless minimal windows were inserted into the solid surface with Georgian proportions, to maintain a seamless transition between the two buildings.