The Swiss Federal Railways’ repair works in Zürich are being lightly transformed for new commercial uses Workers at the Swiss Federal Railways’ (SBB) central repair works in Zürich used to climb the roof of its halls and practise handstands. It was as good a place as any to do gymnastics: out in the open air, with a view to the Käferberg rising across from a tangle of railway tracks and the river Limmat. A photograph from 1947 survives in the SBB archives, showing a light turf growing on the roof – most of the buildings that make up the works had been constructed about 30 years earlier, between 1906 and 1910 – and a group of young apprentices exercising under the stern supervision of a foreman. The photograph captures the beginning of the repair works’ heyday. SBB was formed in 1902, the result of an 1898 referendum to nationalise the nine major private railway companies operating in Switzerland at the time. The construction of the Zürich repair works began soon after, with an office building, a workers’ canteen, shower rooms, workshops, stores and carriage halls laid out across a 42,000m2 site flanked by Hohlstrasse to the south‑west and the railway tracks connecting Zürich Central and Altstetten stations to the north‑east. Here, rolling stock could easily be redirected to the works, and transferred into its functional, skylit brick halls with the use of a lateral transfer platform.  In the postwar decades, the works came to employ upwards of 800 staff, and served as the SBB’s main repair works, or Hauptwerkstätte – there were smaller ones in Bellinzona, Chur, Yverdon-les-Bains and other locations, established by the private railway firms before nationalisation. In the same period, SBB gained international fame for its early electrification drive – the landlocked confederation lacks fossil fuel deposits but has hydropower aplenty – and modern industrial design. The Swiss railway clock, designed in 1944 by SBB employee Hans Hilfiker, is now used in transit systems around the world, and the network’s adoption of Helvetica for its graphic identity in 1978 contributed to the widespread popularisation of the typeface – long before the first iPhone.  At the turn of the millennium, SBB was turned into a joint‑stock company. All shares are owned by the state and the Swiss cantons, but the new company structure allowed the network to behave more like a private enterprise. Part of this restructuring was an appraisal of the network’s sizable real-estate holdings, which a new division, SBB Immobilien, was set up to manage in 2003. Around the same time, the Hauptwerkstätte in Zürich was downgraded to a ‘repair centre’, and plans were drawn up to develop the site, which was vast, central and fashionably post‑industrial – and so ripe for profitable exploitation. The revenue generated by SBB Immobilien has only become more important to the network since then, as its pension fund – long beset by market volatility and continuous restructurings – relies heavily on it. When, in 2017, SBB and the city and canton of Zürich organised a competition for the redevelopment of the old repair works, Swiss architecture practice Baubüro In Situ was selected as winner ‘for its expertise in adaptive reuse, sustainable circular practices and participatory approach’, says an SBB Immobilien spokesperson. For SBB, it was important that the redevelopment, now dubbed Werkstadt Zürich, made use of the railways’ enormous catalogue of existing materials and components. (SBB even has its own online resale platform, where, for example, four tonnes of gravel, a disused train carriage or a stud welding machine can be acquired for a reasonable sum.) For the canton, it was imperative that the scheme make room for local manufacturing in line with a broader drive to bring production back into a city dominated by services.  Founded in Basel by Barbara Buser and Eric Honegger in 1998, Baubüro In Situ (previously Baubüro Mitte) was in a unique position to meet such a brief, as it operates alongside what it terms its three ‘sister companies’: Unterdessen (founded in 2004, to organise ‘meanwhile’ uses for buildings and sites), Zirkular (established in 2020, focusing on materials and circular construction), and Denkstatt Sàrl, an urban think tank run by Buser and Honegger together with Tabea Michaelis and Pascal Biedermann. All informed the masterplan for Werkstadt Zürich, which will complete its first phase this year.  The Zürich offices of the four companies have been housed in various spaces on the repair works site since 2017, while the project has been ongoing. For the past year, they have had a permanent home on a new mezzanine level constructed around the internal perimeter of the works’ cathedral‑like carriage hall. This level is accessed via two central staircases composed of reused components from SBB’s network – I‑beams of various profiles, timber, metal tube railings – which, as has become a trademark of Baubüro In Situ’s work, come together in an artfully mismatched whole. ‘The main thing this office does is as little as possible,’ says Vanessa Gerotto, an interior architect at the firm. SBB still uses parts of the site, as is evident from train tracks that crisscross it. ‘They do repairs in some of the halls,’ explains Gerotto. ‘But they have reorganised, relocated and compacted their repair sites,’ so that approximately 18,450m2 have been freed up for commercial use at Werkstadt Zürich, including a swathe of units in the carriage hall. Here, as in other areas where they are no longer needed, SBB’s tracks have been retained but filled in with concrete and smoothed over.  Businesses have slowly filled Werkstadt Zürich as new units have been completed, and are mostly rarefied, small‑scale producers of luxury consumables: there is a chocolatier, a granola‑maker, a micro‑brewery, a gin distillery and a coffee roastery, as well as a manufacturer of coffee machines. The first commercial tenant, however, was somewhat more in keeping with the original programme of the site: the Swiss outdoor equipment brand Transa moved its repair workshop into one of the spaces in Werkstadt Zürich’s magazine building, to the south of the site, in 2023. Here, a team of 13 craftspeople repair and waterproof Gore-Tex clothing, backpacks, tents and sleeping bags that individual customers either drop off or mail to them, or that official partnering brands send directly to the centre.  ‘The Transa team is currently working on a new set of curtains for the Baubüro In Situ’s offices across the yard’ This part of Werkstadt Zürich was also the first to be renovated. Baubüro In Situ, working closely with colleagues at Zirkular, undertook a substantial interior fit‑out of the triple-height space, located in the western part of the magazine wing. A new timber mezzanine was added to maximise use of the space for the client, who did not require a double-height ground floor space. This was designed to be structurally independent from the shell of the building, so that the listed structure was not impacted.  However, the weight of the mezzanine necessitated new foundations, which needed to support a load of 100kN per timber support. There were not any suitable concrete elements available on site at Werkstadt Zürich, so the teams opted for what Zirkular architect Blanca Gardelegui admits was an ‘experimental’ move, reusing concrete from a demolition site in Winterthur. Here, slabs were cut using a diamond blade saw and stacked on site using a crane. ‘Additional work,’ explains Pascal Angehrn, architect at Baubüro In Situ, ‘came from the temporary storage of the blocks,’ and their transport. Once the blocks had been fitted into place, new concrete nevertheless had to be poured around the timber supports. This meant that, although efforts were made to reuse a wide variety of components and fittings – heaters, doors, plumbing fixtures, lights and stone windowsills – the fit‑out did not meet the architects’ own best‑case scenario of 50 per cent greenhouse gas savings, compared with using new materials and components for the renovation. Instead, they calculated the savings to sit at around 17 per cent. ‘Concrete is one of the most challenging materials to recycle,’ says Gardelegui. ‘The idea is not to do something perfectly, but to learn from the process.’ Finally, the teams introduced a wide staircase into the centre of the space, using the timber from the cut-out mezzanine flooring to make up its steps. Upon moving in, the staff at Transa’s repair centre embraced the architects’ spirit of reuse, creating their own furniture from pallets, and uplholstering with insulation cut‑offs. Tobias Stump, a member of staff at the centre, explains that their team is currently working on a new set of curtains for Baubüro In Situ’s offices across the yard.  ‘The idea is not to do something perfectly, but to learn from the process’ Werkstadt Zürich has the atmosphere of a creative testing ground, where materials get shifted around and reconfigured as needs and uses change. There is genuine camaraderie among the new commercial tenants: they make curtains for each other; organise monthly ‘open factory’ days; and have even recreated the 1947 photograph of the gymnasts on the roof. But antics on the roof may not be viable much longer. The next phase of Werkstadt Zürich involves the construction of vertical extensions atop the halls and magazine wing, densifying the site for further financial gain. Bland, brand new residential towers loom just off site, a little further up Hohlstrasse. Altstetten is gentrifying rapidly, part of the city’s continual remaking of itself.