Cologne attic duplex turns a 1940s roof void into a family apartment

By lifting the ridge line to meet the surrounding roofscape, this Cologne retrofit expands an unused attic into a two-storey home shaped by a three-dimensional grid and defined by a monochrome, sculptural interior.

In central Cologne, an unused attic inside a 1940s apartment building becomes the project’s raw material. The roof is removed and rebuilt with a raised ridge line that aligns with neighbouring heights, pushing the allowable envelope to its limit. The shift is calibrated rather than spectacular: it unlocks one extra level and, with it, a 120-square-metre duplex designed as a compact family apartment stitched into the city’s roofscape.

Inside, the plan is generated from a three-dimensional grid extrapolated from the existing structure, giving each room a distinct, almost sculpted profile. A generous living space runs along the north façade and climbs uninterrupted to the roof, while a central double-height core concentrates the programme, with service areas below and two bedrooms above. To the south, a third bedroom and a roof terrace open toward the courtyard, balancing privacy with daylight. A monochromatic palette sharpens the geometry, reinforcing the apartment’s abstract, volumetric character.

Project Credit

Name: BALTH
Location: Germany, Cologne
Design: Demo Working Group / @demoworkinggroup
Completed: 2024
Photo: Jan Voigt