Accepting Density: Cooperative Housing and the Transformation of Zurich
The Ghost Lines of Densification
In Switzerland, tall thin poles called Bauprofile (building contours) are used to approximate the volume of proposed building projects during planning stages. People unfamiliar with these temporary installations may wonder at their precariousness as they float mid-air, in seemingly arbitrary locations, marking out future volumes in a ghost-like way. Those who already know them enter into informal games of public consultation. Are ‘they’ demolishing that old farm, garage, villa? Will they build over this garden? Will this cut the neighbours’ view? Also, invariably: that high?!! Guesses can lead to formal objection procedures, which after all is the explicit purpose of these devices. On the one hand, they help planning officers assess the impact of proposed developments; on the other, they publicly inform and give notice to those likely to object. In other words, the poles are more than a practical means to an end. By rendering urban planning at once visible and public, they bestow legitimacy on the process.
These days in Zurich the same poles are habitually seen edging close to existing housing. In some cases, they are placed on the buildings’ roofs, indicating the plans for their vertical extension by one or two storeys. More often, however, they hover above or around what seem to be functional, inhabited, sometimes even recently refurbished, apartment blocks, two or three storeys high. In these cases, their placement indicates a condemnation, their impending demolition and the redevelopment of the site. Considered collectively, the massing poles attest to the enormous pressure for more housing in the municipality at all scales. They anticipate the profitable redevelopment of plots previously occupied by houses, the replacement of smaller structures with larger ones and, less frequently, the construction of much higher blocks, placed close together, on the same piece of land. No one can pretend this is merely a matter of the material or typological suitability of the still-standing, soon-to-be-replaced structures. Their desuetude obeys different rules. As brilliantly demonstrated by Daniel Abramson, the notion of architectural obsolescence is tied into real estate logics, which is a means to justify the lucrative redevelopment of sites. Predictably, the concept spread from buildings to neighbourhoods, and from architectural, to urban, scales. This phenomenon of housing preying upon housing, the artificial selection of the most lucrative, is essentially a matter of capital.
The official German term for this practice is the composite word Ersatzneubau (replacement new building), yet the Zurich phenomenon, as explored in a 2018 issue of Werk, Bauen+Wohnen, was presented under the slightly different heading Ersatzwohnbau (replacement housing). The nuance indicates the replacement of existing housing – not tall enough, not closely spaced enough, not capacious enough – with new housing – energy efficient, with an increased number of occupants or dwellings. In Zurich, the existing housing stock is almost fully occupied, and development sites, almost fully built up. The increasing pressure has been translated into a widespread, increasingly controversial strategy of urban densification. The 2014 cantonal report Akzeptanz der Dichte (Accepting Density) showed this to be anything but popular. On the basis of public polls, the report revealed a strong attachment to the existing urban fabric, and resistance to the densification plans put forth by the planners. This tension between political consensus and public opinion has been playing out since, with a variety of outcomes. In a few cases, generally as the result of protracted and expensive legal actions by well-off residents, redevelopment plans have been abandoned.
Such opposition is one of the consequences of steady demographic growth since the late 1990s, with a projected increase of up to 100,000 inhabitants – a quarter of the existing population – by 2040. A partial response to the demographic trends has come with the approval of two municipal laws, ’10,000 Dwellings in 10 years’ (1998–2002) and ’Housing for All’ (2002–06), which buoyed the production of housing, but did not fully satisfy demand. As the Swiss ’Spatial Planning Law’of 2014 limited the expansion of urban areas in order to preserve agricultural land, Zurich’s growth has been delineated within its current limits. With buildable land having reached full capacity, the municipality has embraced densification as the logical strategy, holding the best ‘chance for a sustainable planning’. This agenda has had a further impact on the forms of housing production. If, in 2003, almost 60 percent of the total number of new dwellings were built on previously undeveloped land, in 2020 the figure shrunk to less than four percent. In the mid-2000s, most new dwellings were obtained through change of use from non-residential to residential. The late 2010s’ trend from reconversion to rebuilding/ground densification has seen an inevitable backlash against demolition in the early 2020s. The exhibition Die Schweiz: Ein Abriss (2022) at the Swiss Architecture Museum in Basel, and the series of articles almost identically titled ‘Die Schweiz auf Abriss’, regularly featured in the left-leaning online newspaper Republik (since January 2024) show how the divisive issue of demolition plays out in the public arena. In this context, Zurich now faces the question of how to densify along sustainable lines whilst retaining its urban character. Among Swiss cities, there is no lack of role models. Despite being the largest city in terms of population and area, Zurich’s current density of 4,500 inhabitants per km2 is well under that of Basel (7,200 inhabitants per km2) and Geneva (12,800 inhabitants per km2), both cities of considerable beauty. This suggests that qualitative densification is possible. The challenge faced by Zurich is not whether to densify or why. Rather, where to build and how have become the most urgent questions.
Cooperative Densities
The approximately 50,000 cooperative dwellings currently in Zurich make up 18 percent of the city’s residential stock. Through a series of policies ratified by popular vote, this ratio is set to increase to one-third by 2040. It goes without saying that cooperatives play a key role in Zurich’s race to provide a larger number of affordable dwellings. The pithily titled brochure Dichter (Denser), published by the City of Zurich in 2012, analysed thirty case studies of sites densified by redeveloping built stock perceived as obsolete. Two thirds of the featured projects were owned by cooperatives, followed – in order – by subsidised housing associations, pension funds, and the city. The brochure also illustrated densification efforts overwhelmingly focused on low-density, garden-city settlements in the suburbs. Most of these examples date back to the housing boom of the 1940s and 1950s, which produced the largest number of dwellings the city has yet seen in the peripheral areas of Schwamendingen, Seebach and Oerlikon. One prominent exception was the Kalkbreite cooperative development (2011–2014), a large inner-city perimeter block built atop a functioning tram depot in the central district of Aussersihl. Mehr als Wohnen, another flagship complex of thirteen compact blocks erected on the former industrial district of Hunziker Areal, was another exception to the replacement of existing housing stock. Both illustrate densification through change of use – in Kalkbreite, the superimposition of old and new uses. Most examples, however, show how densification occurs through the replacement of housing by housing. The supplanting of low-rise, anonymous, modular residential buildings with blocks that are taller, larger, more capacious have rendered the suburbs more urban. The loss of privacy and green spaces is compensated by the introduction of modern amenities, such as better kitchens and larger balconies, by energy-efficient construction and, arguably, the impression of a more central, better connected location.
The Dichter brochure signals the extent to which housing cooperatives play a central role in the recent wave of urban densification.As non-profit, collective forms of ownership, cooperatives have formed the backbone of the city’s affordable housing policy since the early 1900s, assuming the function of social or public housing providers under different welfare regimes. Since 1907, the cooperative movement has been statutorily strengthened by a long-standing partnership with the city of Zurich, an alliance that continues to this day. Whilst cooperatives originated from niche middle-class experiments in the 1890s and early 1900, a series of municipal policies between 1907 and 1924 rendered cooperative living increasingly affordable. Advantageous financial arrangements, ratified by a series of popular referendums, lowered the equity for cooperatives, first to ten percent in 1910, then less than six percent in 1924. The city controls the essential incentive of providing leases to build cooperative housing on municipal land, both in the inner city and in the periphery. These financial and real estate practices continue to this day, having allowed housing cooperatives to grow in size and number. For several decades, they have sustained the city’s manufacturing economy by providing cooperative homes for its working-class inhabitants.
In the neighbourhoods of Aussersihl and Industriequartier – within walking distance of the industries themselves – the older cooperatives were identified with dignified, large-scale perimeter blocks called Wohnkolonie, with inner courtyards landscaped as gardens and playgrounds. Contrasting with the piecemeal speculative developments around them, these large blocks of the 1920s and 1930s had a significant impact on the city fabric. However monumental, this urban type was nevertheless dwarfed by the number of low-rise blocks and terraced rows built after the 1934 annexation of eight peripheral communes. The additional ground was largely leased to cooperatives, ushering in the frenzied construction of suburban housing settlements in the 1940s and 1950s. Uniformly planned as nuclear family dwellings in mono-functional clusters, today they are underoccupied and outdated. With the necessary reconditioning works, the postwar housing production has become prime material for the current densification efforts.
Cooperative generations and specializations
A curious and, I believe, time-sensitive feature of Zurich’s cooperatives at the start of the 2020s is that one can reliably infer their historical age and ideological background from their organisation, dwelling types and non-residential functions. Relatively conservative, the older cooperatives are almost always exclusively residential, and focused on providing nuclear family dwellings in a variety of sizes. They invite less participative inputs from tenants, are less likely to provide public facilities and communal functions or areas. Therefore, many of the densification efforts in the suburban areas, where the ground lease or ownership remains in the hands of the cooperatives that developed them in the first place, result in relatively mono-functional, insular residential ensembles. By contrast, newer cooperatives such as KraftWerk1, Kalkbreite and Mehr als Wohnen are demonstrably experimental, prioritising a great range of dwelling typologies and collective functions, as well as insisting on a more urban pluri-functional approach. Resulting directly from the social movements and squatting scene that exploded in Zurich in the 1980s, this younger generation of housing cooperatives distinguishes itself from the established model for its renewed insistence on self-governance and participation, and for placing sustainability at the centre of its building and operational activities. From shared resources and collective spaces, sustainability extends to stringent performance credentials in construction and inhabitation, and, especially relevant for the current discussion, to the efficient use of inhabitable space. The environmental commitment of the new cooperatives also translates into an explicit concern with densification. Rather than residential settlements, the new cooperatives aim to create urban neighbourhoods. Programmatic slogans, such as Kalkbreite’s ein Stück Stadt(a piece of the city) or, indeed, Mehr als Wohnen (more than housing), indicate an ideological commitment to the idea of urbanity. This translates in the principle of the public ground floor: commercial services and collective functions are concentrated at street level, creating opportunities for social interaction and assuring the urban porosity of the cooperative ensemble. At the same time, the involvement of residents is often geared towards sustainability-related issues, with parts of the communal areas at ground or roof level dedicated to communal growing areas.
More subtly, the new cooperatives have come to claim certain specializations. These are deeply rooted not only in the specific circumstances of their creation, but also their locations in the city, and the different strategies these dictate. Thus Wogeno, established in 1981 in protest against real estate speculation, mostly focuses on reconditioning existing properties as they become available in various locations in Zurich and its surrounding area, including the city of Winterthur. The cooperative Dreieck, established in 1996 with the specific aim of preserving the original fabric and the residential community of a nineteenth-century perimeter block in Aussersihl, has overseen not only the renovation and preservation of original buildings, but also the sensitive insertion of new apartment buildings completing the original block. Kalkbreite, initially a neighbourhood association, transitioned to cooperative status in 2008 in order to densify a contested site atop a functioning tram depot in Aussersihl. On the back of the success of its flagship building, by Müller Sigrist, the cooperative won the lease for another development near the main railway station, Zollhaus. Designed by Enzmann Fischer and completed in 2020, Zollhaus incorporates public and commercial functions as well as a great variety of experimental dwelling types, aimed explicitly at lowering the surface area per capita.
Indeed, the agenda of densification dictates manycooperative portfolios and modi operandi. The issue of density becomes particularly striking in the case of the newer cooperatives that operate on the city’s periphery. KraftWerk1, a pioneer of collective dwelling typologies established in 1996, is best known for developing dense estates on former industrial sites. Its first ensemble, designed by Bünzli Courvoisier and combining housing, live-work spaces, offices and shops, is located in Hardturmstrasse. This project was followed in 2012 by Heizenholz, in Höngg, a multi-generational living collective designed by Adrien Streich, formed by extending and connecting two small residential blocks. Closer to the notion of Anbau (a later addition to an existing structure) it represents an ingenious and more sustainable form of densification. Zwicky Süd is the cooperative’s third completed project, designed by Schneider Studer Primas. This extremely dense settlement in the fast-growing suburb of Dübendorf anticipates the densification and urban growth that will occur in the area in the next two to three decades. Like Mehr Als Wohnen in Hunziker Areal, these examples illustrate the densification of disused industrial precincts – in contrast to the older suburban cooperatives, which tend to replace older, smaller housing with units that are denser and larger. The provision of public functions, such as restaurants, shops and hotels, depends upon the custom of locals and residents more than visitors and passers-by. The cooperatives’ declared ambition to create dense, lively neighbourhoods is at odds with their current isolation from built-up areas.
Density and the cooperative interior
The drive for densification is intimately connected with the development of the cooperative interior. Once considered as a non-negotiable standard, the family dwelling with one, two or three bedrooms provided by the historical cooperatives has in the twenty-first century been challenged by the emergence of innovative and experimental dwelling types. These, in turn, are the result of innovative perspectives on collective living, based on the unlikely confluence of the cooperative tradition with the youth movements of the 1980s. The illegal squats and urban occupations of the time, whilst permanently precarious and the target of inevitable clearance by the police, were fertile ground for developing new types of collective dwelling. The association Karthago, established in 1986, after the forceful eviction of squatters from unoccupied properties at Stauffacher in 1984, envisaged the creation of autonomous collectives with shared ‘public’ areas such as dining halls, roof terraces and living areas, but also with ‘flexible living zones of 6-10 people’, mixing communal living areas and individual rooms:
As many walls as possible have been removed and replaced by sliding walls. Each resident decides on the colour of their walls. The rooms are mostly empty, without furniture. In each inhabited room, an object is displayed on a white block and changed every day. Beds, cushions, sleeping mats, objects of daily use, clothes, etc. are placed in large wall cabinets. The floors, some of which are closed and some of which are carpeted, are only to be walked on barefoot, in socks or slippers. … In the evening the cupboards are opened and a lot of colourful cushions, decks, games, cups, are poured out. (Where there are children, perhaps also during the day).
Karthago’s squatting experiments with collective living were the first in a series of developments that eventually led to the ‘cluster’-type dwelling introduced in many younger cooperatives as the counterpart to the traditional family apartment. As changes in society have dictated an interest in more complex mixtures of flats, cooperatives have led the experimentation with multiple scenarios for collective living, including informal communes, patchwork or multi-local families, generation and collective accommodations for singles and the elderly. The great majority of cooperative flats in Zurich constrain rentable flat size according to household size, which has incentivized cooperatives to consider the most efficient flat sizes in their housing stock. Alongside the cluster apartments, which despite their space efficiency are more expensive to build and more arduous to organise than family dwellings, another innovative type is the Hallenwohnung, a loft-style collective unit based on the example of squatters’ adaptation of industrial spaces to residential use. Whatever the types provided, however, the provision of a wide range of apartment types and sizes, with generous collective spaces, is tied in with the principles of space efficiency, and thus, to density. By voluntarily reducing the living surface per inhabitant, cooperatives seek to reduce both costs and environmental impact, and share the same footprint among a larger number of residents.
Density as urbanity
As cities across Europe are facing the challenges of densification, Zurich’s anticipated, accelerated growth over the next decades will be closely watched. In this scenario, cooperative housing, whether historical or current, plays an important part in the preservation of the city’s high quality of life and architecture. The frequency and location of Bauprofile on Zurich’s existing and planned housing corroborates this thesis: a physically flimsy, yet reliable, type of evidence.
Judging by the absence of these tell-tale precursors of redevelopment, it would appear that the more central Wohnkolonien, the historical inner-city cooperative blocks, are relatively impervious to twenty-first century densification attempts. By means of their scale, architecture and urban qualities, they define the character of neighbourhoods and entire districts. Dense to begin with, they cannot easily increase their bulk. They can be either listed and sensitively restored, or remain vulnerable to being replaced. Less extreme cases show the potential of refurbishment to correct the shortcomings of older housing stock, but not to increase its density. The standard local practice of adding large balconies to courtyard facades, whilst greatly improving apartment layouts, has no significant impact on the numbers of inhabitants. Other cooperative estates, however, are more vulnerable. The scenario of replacement – Ersatzneubau – is considered also in the city centre, as shown by the proposed and seemingly ongoing rebuilding of ABZ’s historical Siedlung Kanzleistrasse in Aussersihl, which will double the number of inhabitants. As witnessed by the ubiquitous, hovering Bauprofile, the buildings earmarked for demolition urgently raise the question of irreversible damage to the city’s historical fabric. What are the redevelopment criteria in the case of structurally sound, decent historical buildings endangered by the densification rush? The strategy of Ersatzneubau comes up against their value as historical heritage, a poignant illustration of the issues raised by architectural obsolescence.
The argument of historical value is harder to invoke in the case of the suburbs of Schwamendingen, Seebach, Affoltern, Altstetten and Albisrieden, where the prevalent ordinariness of postwar prefabricated blocks has more easily led to redevelopment. Since the early 2000s, a spate of architectural competitions has changed the character of these outlying neighbourhoods beyond recognition. The city keeps a close tally of the densification achieved through the replacement of existing residential buildings and entire housing estates. On average, from 2015 to 2019, there has been a degree of densification of 70 percent, with each demolished flat replaced by 1.7 new flats, and an increase of 112 percent in the size of dwellings. The densification is particularly marked in public and cooperative housing, where the number of residents has doubled during the same interval.
The question that statistics do not address is that of the quality and character of the new, full-fledged urban quarters resulting from the gradual transformation of the suburbs. Slowly, the city does away with sprawl and densifies up to its limits, which is likely to lead to starker contrasts and increasingly abrupt transitions between built-up, multi-storey building areas and the surrounding countryside. Architectural competitions need to tread a fine line between solutions that are effective at the level of buildings (apartment types and orientations, plan layouts, communal amenities, etc.), and decisions that have an impact at urban scale: the buildings’ massing and formal articulations in relation to their surrounds, their materiality and physiognomy. Particularly in areas of considerable redevelopment, the appearance and urban typology of the new projects is increasingly relativised. Without being anchored into stable existing settings, they run the risk of becoming generic. In these areas, the focus on buildings or ensembles of buildings at the level of the individual project needs to be balanced by an overall vision and enshrined in urban codes. As argued by Daniel Kurz: ‘as long as every new settlement is planned as an island in an unmanageable archipelago, the greater whole is neglected. We must advocate a massive broadening of the scope of urban planning.’ For a qualitative densification to occur, planning processes must expand and negotiate more freely between the scale of individual buildings and that of the city. An intermediate scale, that of the neighbourhood, needs to be activated, and default demolition needs to be replaced by more refined, fine-grained strategies of intervention. Only then will density be accepted.
Architect and historian Irina Davidovici is the Director of the gta Archiv and Senior Scientist at ETH Zurich. Her research straddles housing studies and modes of transmission of architectural knowledge. She obtained her doctorate in the history and philosophy of architecture from the University of Cambridge (2008), Habilitation at ETH Zurich (2020), and led the gta doctoral programme in the History and Theory of Architecture until 2021. Davidovici was senior lecturer at Kingston University, London (2008–13), SNF Marie Heim-Vögtlin Fellow (2014–16) at ETH Zurich, Harvard GSD Richard Rogers Fellow (2018), gta Postdoctoral Fellow (2016–17), and visiting professor at EPFL Lausanne (2020–21). She is the author of Forms of Practice: German-Swiss Architecture 1980–2000 (gta 2012 and 2018) and The Autonomy of Theory: Ticino Architecture and its Critical Reception (gta, 2024), and edited Colquhounery. Alan Colquhoun from Bricolage to Myth (AA, 2015).
