In 1991, the practice designed a masterplan for the reinvention of a 89-hectare site in Duisburg’s Inner Harbour – the largest inland harbour in the world. The Inner Harbour masterplan reconnects the water with the centre of the Ruhr valley city, transforming an industrial landscape in decline into a thriving, mixed-use urban quarter. Combining the selective refurbishment of existing structures with new construction, a high proportion of the development is residential and its mixture of housing types includes the NF1 low-cost rental apartments.

Designed for Duisburg’s regional housing association, the NF1 apartment building is arranged as a terrace of nine interconnected volumes along Philosophenweg, the ‘philosophers walk’ that runs between two canals. The design concept reflects the industrial character of the retained warehouses to the north and contemporary residential developments and park to the south by alternating opaque and transparent materials: the northern elevation is more solid, clad with terracotta tiles in a colour that matches the bricks of the retained grain store buildings, while the southern facades are fully glazed, shaded by horizontal brise-soleil. The apartments are oriented north-south, with living and dining areas on the light-filled south side and bedrooms to the north. The majority of the 68 apartments are single-storey, available in two sizes. Larger duplex apartments, with double-height living spaces, are placed on the upper floors and angled corner of each building.

Each ground-floor apartment has its own terrace or winter garden. In winter, the spaces contribute to the building’s environmental strategy by providing an additional thermal barrier. During spring and autumn the gardens can be integrated with the living space by opening an internal glass sliding wall, while in summer, further full-height sliding windows fully connect inside and outside space, maximising the useable area. Heat is provided by the district heating network and rainwater is collected and discharged to the nearby canal, where it is filtered and circulated as part of the wider water system for the masterplan.