The £1.7 million project consists of a ground-floor rear extension with restoration to internal fixtures
Gibson Thornley has refurbished a Grade II-listed Georgian townhouse at 5 Charterhouse Square. The architect aimed to reinstate the original plan and hierarchy of the building, which was adapted from residential to office use in the 1930s.
As well as the extension, the project comprised restructuring the basement and vaults to provide shower and locker facilities, providing additional meeting rooms, and creating external lightwells to draw natural light in.
Upper floor office accommodation occupies carefully restored rooms within the original building, with all-timber panelling and cornicing refurbished or replaced. Each space is equipped with heating and cooling that is integrated into the timber panelling. A series of kitchens is located within the original closet wings, providing facilities for catering and hospitality.
The new boardroom extension features a timber-lined wall that transforms into a series of dramatic, ribbed soffits. White-painted steel ribs create an ’exoskeleton’ with glazed panels that open up the room to an external landscaped terrace and draw natural light down from above.
The remodelling of 5 Charterhouse Square combines a faithful restoration of the Grade II-listed townhouse with a contemporary extension and re-appropriation of what would otherwise be marginal spaces at basement and attic level. Originally constructed in 1697, the property had undergone a series of changes during its 300-year history, not least a rather clumsy series of adaptions in the 1980s which served to undermine the integrity of the original house.
By undertaking research into the original plan-form and detailing of the property, the Georgian hierarchy and interior have been recaptured to create a series of graceful spaces for office use. The development capitalises on the building’s heritage assets, creating a sensitive and historically appropriate series of rooms.
The extension reinterprets the anatomy of a Georgian interior (timber wall panelling, window threshold) to create something contemporary while being borne out of the specificity of its context. New shower, drying room and locker facilities have been provided within the basement vaults, equipping the property with the provision that one has come to expect in contemporary workplaces.
The careful integration of services has been done sensitively and, in so doing, has enhanced (rather than hamper) the historic interior – liberating it from wall-mounted radiators, sockets and switches. 5 Charterhouse Square has been remade, creating an enduring property befitting of its heritage. A series of highly serviced, loose-fit spaces enable the building to be occupied in a flexible way that can evolve over time.
Ben Gibson, director, Gibson Thornley Architects
Start on site May 2017
Completion October 2018
Gross internal floor area 609m²
Gross (internal + external) floor area 641m²
Form of contract JCT Standard Building Contract
Construction cost £1.7 million
Construction cost per m² £2,826
Architect Gibson Thornley
Client The Charterhouse
Employer’s agent Ingleby Trice
Structural engineer Symmetrys
M&E consultant XC02 Energy
Lighting consultant DHA Designs
Heritage consultant Dorian Crone
Party wall surveyor Trehame Building Consultancy
CDM advisor Shore Engineering
Approved building inspector MLM
Main contractor Forcia Limited
CAD software used MicroStation