Concrete, glass, and steel are used to great effect in the construction of Reciprocal House, a newly completed 280-square-meter (3,014-square-feet) family home designed by London-based Gianni Botsford Architects. Located in a leafy Hampstead mews in north-west London, the home is hidden behind a Victorian pub. Reciprocal House replaces a nondescript, run-down coach house and its smart and robust design responds to an adjoining 1969 extension by Foster Associates (now Foster + Partners).*
Former coach house:
Foster Associates’ lightweight, single-story extension is made up of steel trusses, concrete blocks, and large-span aluminum-framed glazing (its splendid midcentury appeal is captured in the original image below). Gianni Botsford Architects’ design for the four-story Reciprocal House responds to the extension’s industrial character, “essentially extending the extension,” says Gianni Botsford. The architect has returned the extension to its original state, creating a “reciprocal relationship” between the 1969 structure and newly built house by using a limited palette of timeless materials: concrete, glass, and steel.
Original 1969 extension by Foster Associates:
Original extension by Foster Associates (pictured in 2022):
The revamped extension (originally a place for entertaining) is part of the home’s bright, open-plan ground floor and includes the kitchen, dining, and living spaces; the two upper floors house three bedrooms and a roof terrace; a basement studio benefits from three-meter-high light wells.
Gianni Botsford Architects designed the home’s highly crafted and bespoke aluminum component’s: the staircase, kitchen units, wardrobes, bathroom fittings, screens, and doors. These components were fabricated by south-east London-based Weber Industries.
Gianni Botsford Architects made a series of physical study models to examine the site as well as the relationship between both the new house and the Foster Associates extension. “This led to an approach whereby the form and volumes of new and old elements of the project were both of similar architectural stature yet clearly delineated in the design,” says Botsford. The models also encouraged the studio to assess the home’s relationship with its surroundings, in particular the mature trees that border the 56-square-meter (603-square-feet) roof terrace.
Reciprocal House evokes the roof profile of the original coach house, while the architecture’s distinctive angled elevations impart a wonderfully geometric quality both externally and internally — “perforated aluminum sail-like roofs control privacy as well as preserving a memory of the original building,” says Botsford. The perforated aluminum’s soft copper-brown hue blends with the leafy nature — in addition to offering privacy, the mesh also provides protection from solar gain and acoustic separation.
Gianni Botsford Architects made the decision to construct the new dwelling in concrete owing to its “complex form”. To reduce the use of finishes, the concrete remains visually exposed, enhancing the home’s robust character. “The structure of the new house is optimized to allow for the thinnest possible wall and floor build-ups,” says Botsford. A circular roof light is positioned above a sculptural aluminum spiral staircase that connects the three main floors. The roof light can be fully opened to provide natural ventilation.
The project is designed to minimize its environmental impact and incorporates passive design techniques: tall trees that surround the house provide natural shade from solar gain; the size and orientation of windows maximizes both natural light and ventilation; the spiral staircase acts as a vertical ventilation shaft — in conjunction with the openable roof light, it uses a natural stack effect to push hot air out and draw cool air in.
Gianni Botsford Architects made use of materials with a high thermal mass, exposed concrete in particular — combined with natural ventilation, this helps the house to stay cool without the need for active cooling.
The house is heated via an acoustically attenuated air source heat pump and underfloor heating, however enhanced thermal insulation and air tightness reduces the need for space heating. Gas burning appliances have not been installed in the kitchen.
Water consumption is reduced with the use of low-flow fittings; shower and bath water is treated by a grey water recycling system and reused for toilet flushing; rainwater recycling and green roofs also help to reduce water consumption and run-off.
The home’s landscaping utilizes demolished brickwork from the original house, playing on the notion of “embodied memory” while repurposing existing materials.
Reflecting on the project, Gianni Botsford says: “Through the process of reinvention, the evolution of the retained, demolished, and newly built structures speak to architectural history, layering, and respect.”
*The project architect for the extension by Foster Associates was Patty Hopkins who later established Hopkins Architects with Michael Hopkins in 1976.
