How to create an extra 140 m² of space in the heart of London? Simply build on the roof. Atop the offices of The Architecture Foundation and think tank Demos, David Kohn Architects has built a partly cantilevered rooftop enclosure, suitable for outdoor events. The structure is set around a central courtyard space from which four niche areas of different sizes protrude. Featuring both open and covered areas, the roof terrace offers an event venue for The Architecture Foundation, yet also provides a social space for the remaining tenants of the five-storey building. As the original roof structure could take no extra weight, the lightest of materials were used to construct Skyroom, including white steel, stainless steel and copper mesh panels. A material developed by NASA to create enclosures on the moon, ETFE (Ethylene Tetrafluoroethylene) cushions cover certain parts of the enclosure, while the courtyard area is left open to the sky.