15 Mansfield Street

15 Mansfield Street is a Grade II-listed building in the Marylebone Conservation Area, refurbished and extended to provide high-quality office accommodation. The project involved a comprehensive remodelling of the existing building, including alterations to the core, circulation and stairwell, alongside the replacement of the existing roof with a new mansard extension.

The new storey is designed in keeping with the character of the original building, while the refurbishment carefully retains and enhances its 18th-century features. New double-glazed sash windows set within the original frames improve the building’s energy performance, achieving an EPC B rating without altering its historic street elevation.