The story begins in 1969, when Foster Associates designed a single-storey extension to an unassuming 1860s coach house. Intended as a space for entertaining, the light-framed addition was conceived under Norman Foster’s direction, with Patty Hopkins as project architect, and embodied the experimental spirit of Britain’s emerging high-tech movement, combining steel trusses, concrete block walls and wide aluminium-framed glazing. By contrast, the original structure was of little architectural or aesthetic value, and in a rather dilapidated state, so when Gianni Botsford Architects were commissioned to renovate the property, it was decided to demolish it and replace it with a new building, effectively an extension to Foster’s extension.

The new building’s design was informed by a multitude of constraints related to providing privacy for both occupants and neighbours, long views across neighbouring back gardens, access to daylight, acoustic separation and security, not to mention the presence of mature trees that limited its footrprint. To reconcile these sometimes competing priorities, Gianni Botsford Architects developed a series of physical study models, using them to test the form, massing, and sightlines of the new building in relation to the retained extension. This process guided the design toward what the architects describe as a “strong sense of reciprocity” between the two structures which they envisioned as equal in stature, yet distinct in expression. The three-storey trapezoidal structure that emerged from that investigative process introduces a sculptural counterpoint to Foster’ boxy extension while nodding to the pitched roof of the demolished cottage.

Unfolding across four levels, the house accommodates three bedrooms on the upper floors and a basement studio, generously illuminated by deep lightwells, with communal areas on the ground floor where old and new converge in a single open-plan expanse. Meticulously restored to its original design, Foster Associates’ extension now functions as a living room, while the new addition houses the kitchen and dining area, a small difference in floor level, just two shallow steps, marking the seam between eras. Though conceived as one continuous space, this subtle shift in elevation, together with variations in ceiling treatment, preserves each structure’s identity while allowing light, perspective, and movement to flow freely between them. Above, the roof of the original extension doubles as a terrace for the new bedrooms, extending this sense of reciprocity into the vertical dimension.