Potenzialanalyse zur Umnutzung von Büro- und Gewerbeflächen zu Wohnraum in der Stadt Basel (Vertiefungsbericht)

The study Potenzialanalyse zur Umnutzung von Büro‑ und Gewerbeflächen zu Wohnraum in der Stadt Basel (Vertiefungsbericht) was commissioned by the Department of Urban Development of the Canton of Basel‑Stadt and prepared by the consultancy Wüest & Partner (Martin Hofer, Daniel Romer). It investigates the conversion potential of vacant office and commercial spaces into residential units in Basel, drawing on data from the 2011 SVIT vacancy survey and supplementary market analyses. The report was completed in January 2013 after field work between December 2011 and June 2012.

In June 2011, roughly 75 000 m² of office space and 21 000 m² of commercial/production space were reported vacant across the canton. Within the city centre, about 29 170 m² of office space and 10 840 m² of commercial space were empty, while outside the centre the vacancy amounted to approximately 45 500 m² of office space and 10 000 m² of commercial space. After excluding newly built but unoccupied units, the net “usable” vacancy outside the inner city is estimated at 56 000 m² of office space and 6 600 m² of commercial space.

Applying a 60 % conversion factor, the authors calculate that around 24 000 m² of office and commercial floors could realistically be transformed into housing. Assuming an average dwelling size of 100 m², this translates into roughly 240 new apartments. Additional “life‑science” relocations (Novartis and Roche) are expected to release another 13 300 m² of office area by 2016; if half of this becomes available for housing, a further 6 500 m² (≈ 65 units) could be added. Overall, the study projects the creation of 400‑600 new homes over the next fifteen years from office‑to‑residential conversions in Basel‑Stadt.

The report distinguishes between conversion to rental apartments and to owner‑occupied units. Rental conversion is deemed economically viable only where the rent differential exceeds CHF 2 000 per m² per year; no city quarter meets this threshold in the aggregated analysis. Conversely, conversion to ownership is financially attractive where the price differential surpasses CHF 3 000 per m² per year, a condition satisfied in most outer‑city quarters and in the municipalities of Riehen and Bettingen. Typical conversion costs are estimated at CHF 2 000‑3 000 per m², compared with new‑build costs of CHF 3 000‑4 000 per m².

Office rent yields in Basel generally exceed residential yields, making direct office use more profitable where demand remains. However, many peripheral office locations experience below‑market rents, creating a mismatch that supports conversion. Median office rents in the city centre (≈ CHF 261/m²·a) are lower than in some outer quarters, while median residential rents often surpass office rates, especially in second‑class office districts such as Breite/St. Alban and Kleinbasel Ost.

The most promising conversion sites are located outside the inner city, particularly in the districts of Breite/St. Alban, Gundeldingen, Basel‑Bachletten/Gotthelf, Iselin, St. Johann, Kleinbasel Ost, and the neighbouring municipalities of Riehen and Bettingen. In contrast, the central district and high‑value office zones (e.g., Bruderholz) show limited economic incentive for conversion due to higher office rents and lower residential price differentials.

From a technical standpoint, the majority of office and commercial buildings meet basic conversion criteria: typical building depths under 16 m, ceiling heights between 2.6 m and 3.5 m, adequate structural capacity, and existing service infrastructure. Specific constraints arise in deep or highly specialised office blocks, which may require additional engineering measures.

Converting existing office stock reduces the need for new construction, lessening material consumption, embodied carbon, and urban sprawl. By re‑using built‑up areas, the project aligns with sustainable urban development goals, supporting higher residential density without expanding the city footprint. The identified 400‑600 potential dwellings could alleviate housing pressure while preserving green spaces around Basel.

The authors suggest targeted incentives for owner‑occupied conversions in outer districts, streamlined zoning adjustments where necessary, and continued monitoring of office vacancy trends. Collaboration with private owners, especially institutional investors, is essential to unlock the identified conversion potential and to ensure that the transition contributes effectively to Basel’s long‑term housing sustainability.