Sam Rosenzweig
Ashoka Elected in 2021   |   Belgium

Sam Rosenzweig

Communa is spreading the concept of “Temporary Use with a Social Purpose” across Europe, as a new norm of using vacant buildings at the service of local communities and citizen sector organizations.…
Read more
Because of the pandemic, Sam Rosenzweig was selected by Ashoka as a Special Relationship (Virtual) using an online process.


Communa is spreading the concept of “Temporary Use with a Social Purpose” across Europe, as a new norm of using vacant buildings at the service of local communities and citizen sector organizations. By empowering local communities to blueprint the future function of vacant buildings, they influence the property owner’s mindset to create more resilient, inclusive, and citizen-run cities.

The New Idea

All across Europe increasing numbers of buildings are left vacant, while at the same time, space to rent and live becomes increasingly expensive. These developments exclude a growing number of people in precarious living situations in urban areas. As a response, Sâm and Maxime created Communa to professionalize and organize the field of temporary use on a European level to make it the default model for cities to leverage vacant spaces to serve its inhabitants. They have coined the concept of so-called “Temporary Use with a Social Purpose” (TUSP), which consists of temporarily using vacant office or housing buildings, owned by private or public actors, to serve local communities’ and especially vulnerable population’s needs. Communa has developed the legal, financial, and technical framework to make TUSP operational and is spreading this model across Europe by organizing a growing international community comprised of citizen sector initiatives from eight different European countries. This community wants to provide social purpose to vacant space and use it as a lever to create new blueprints of urban democracy to create more inclusive and just cities that function in solidarity.

Through their TUSP model, they are also reinforcing the role of a key, but often neglected stakeholder in the urban planning process – the local communities that are living and working around the vacant buildings. After having signed a legal agreement with the owners, to use the empty buildings free of charge, Communa empowers the communities by giving them the responsibility to decide how to best use the space so that it first serves the needs of the inhabitants. Deeply anchored in its environment, the local community is able to identify, articulate and fulfil specific needs of the neighborhood, such as providing housing to people in need (refugees or homeless people), (re)creating social links, organizing intergenerational interactions, offering affordable space to social entrepreneurs or artists, developing circular economies, etc. Thanks to this TUSP model, communities can have a say in urban planning activities: Communa supports them to create a longer-term impact on the future use of the building by working with the public and private property owners to influence their ultimate plans, applying temporary use as an experiment to foreshadow the potential end function of a vacant building.

Indeed, for Maxime and Sâm, temporary use is only a means of achieving long-term change in how public and private actors’ imagination in regard to the purpose of their buildings by demonstrating at a very low cost the positive impact that spaces of local community innovation and cohesion can have. Their vision is to create a mindset amongst public and private property owners of seeing the functions of buildings not as fixed but in a permanent transition that best capture the evolving needs of neighborhoods. Their temporary use serves as a means to create a ‘permanently temporary’ mindset amongst all stakeholders.

Through its activities on 12 currently active sites, which provide temporary use opportunities for more than 200 neighborhood and social organizations in Brussels, Communa is increasing the demand for more temporary use of vacant spaces with a social purpose by collecting, measuring, and sharing knowledge that makes this model attractive for new actors, such as real estate developers and city governments. Indeed, these public and private actors are struggling to find adequate responses to deal with vacant buildings in an appropriate manner and Communa’s innovative approach to urban planning constitutes an efficient answer for them. Having already achieved regional recognition by the Brussels government, which included the spreading of their TUSP model in their urban planning policies to make it easier for social organizations to use vacant buildings for housing or engagement of their target groups (e.g. refugees or homeless), they are now working on collaborating more closely with organizations in the other Belgian regions of Wallonia and Flanders and across Europe to spread a new, structured model to support cities.

The Problem

The emergence of ever more globalized cities governed by austerity driven public services and the profit interests of real estate investors are leading cities to become increasingly commodified. Spaces now need to generate a profit, or at least serve to enable people’s profit generation. This impacts the housing situations of the most fragile populations as numerous citizens cannot find access to decent housing due to their lack of financial resources, their administrative situation, and the unsuitability of the social housing offer. In Brussels alone, the number of families waiting for social housing has increased over the last ten years to 46,000 (approximately 125.000 people) even though 1500 social housing opportunities are being built annually, highlighting a severe housing crisis in the Belgian capital. This shortage also impacts the social and cultural sectors, as artists and non-profit organization struggle to afford workspaces in cities.

At the same time, the increasing number of vacant spaces within cities can be observed all across Europe. According to studies by both the European Commission and the OECD, approximately 1 out of 6 properties are left vacant in Europe. The increasing rates of working from home, the creation of shopping malls outside of city centers, and increasing online shopping activities all re-enforce the desertification of cities. In Brussels alone, 6,500,000 square meters of buildings and offices spaces are empty at this moment. In the Brussels region, leaving a building empty for more than one year is considered illegal with hefty fines imposed on owners (formula to calculate the annual fine: 500€/year x length of the façade x number of floors. For a one family home this is 6000€ per year). At the same time occupying or squatting vacant spaces is also highly penalized (squatting is seen as a criminal act that can lead to imprisonment).

In this time of unmatched supply and demand, the traditional urban planning stakeholders have not found the right answers. Urban planning practices remain opaque, top-down and do not foster citizen participation to directly tackle the needs of the (new) populations. Indeed, public authorities tend to consider inhabitants as not having a relevant point of view on urbanistic questions. At the same time public decision-making processes take a long-time, leading to spaces being left vacant by public authorities while they decide how to use the building in the long run. For the private sector, increased financialization of the real estate market has made it lucrative to leave buildings empty for speculative reasons, a trend that can be observed across European cities that not only produces vacant buildings, but also increases rent price and decreases living space for citizens.

So far, the citizen sector has reacted with un-coordinated and illegal occupation and squatting practices to allow vulnerable populations access to space on highly precarious terms and conditions. This has led to increased tensions instead of constructive solutions between property owners, city governments and civil society actors.

The Strategy

In this period of unmatched supply and demand of vacant space, increasing difficulties for citizens to find decent spaces to live and work, and lack of constructive solutions on behalf of the civil, private, and public sectors, Communa is changing the way we see cities. Instead of a commodity, they see the city as a common, in which the citizens can decide what function the city should fulfil instead of the citizen following the often-economic function of the city. To realize this vision, they are pursuing a four-fold strategy of spreading their idea of temporary use with a social purpose (TUSP).

Firstly, they show at first sight how temporary use activities can turn into permanent activities within a neighborhood by running TUSP projects themselves. Secondly, to scale their work, they are creating and spreading tools to empower stakeholders to make use of TUSP. Thirdly, they are building the legitimacy of TUSP through advocacy and political lobbying. Lastly, and building upon the first two elements, they are working to ensure that the aforementioned elements are translated into regulation and institutionally adopted.

Maxime and Sâm use Brussels as their laboratory to showcase other ways of designing a city, while also respecting its social fiber through the application of temporary use as a prototyping tool. This way, they test and refine their models, while also developing proof of concept and impact. For Maxime and Sâm, empty spaces represent the opportunity to create prototypes that surface citizens’ needs and demonstrate how buildings should be generally conceived, considered, and used. To make this possible in Brussels and beyond, they have developed a guide from A to Z, to create self-governing communities to run the buildings and have also built the correct legal and technical frameworks to replicate their model. Their process not only involves citizens wanting to use empty spaces, but also actively engages the owner so they can play a role and see the advantages of allowing their space to be used for the good of all.

At the start of all of their projects in empty buildings, Sâm and Maxime sign an agreement of temporary use with a social purpose with the building’s owner (private or public), which serve as the conditions of use throughout an agreed-upon time period. Communa is ensuring security for the future tenants by making small-scale renovations. For this they collaborate with local social entrepreneurs and only use reusable materials that they can use for future TUSP activities in other buildings. The TUSP agreement, ensures for the owners that they will not need to pay penalties as their building is not empty anymore in use and ensures for Communa the rent-free use of the space for a guaranteed period of time in which they aim to make the temporary permanent.

To guarantee that the needs of the neighborhood are met, Maxime and Sâm make the creation of communities of local inhabitants within the buildings a matter of priority, as these communities are the best positioned to create adequate activities and run the space. As a first step, they invite residents and relevant stakeholders as social organizations to share their ideas on how the space shall be used and what projects they would like to realize. Then they facilitate a democratic decision-making process to collectively decide what kinds of projects should be implemented to serve the local community and identify the future tenants of the place (be they individuals or organizations). This ensures that there is ownership of the community projects amongst the tenants of the space from early on. Ultimately, they involve the tenants in the overall management of the building by equipping them with democratic tools enabling them to self-organize and run the place independently.

Throughout this process they document the evolution of the project and involve the property owner at regular community meetings, so that they understand the community’s needs and what the building’s set-up could look like to serve them in the longer term. Therefore, at the core of the TUSP model lies the idea that temporary use can have an influence on the permanent function of a building, by shifting the property owner’s mindset away from pre-determining a building’s function without involving the community that surrounds it. By temporarily using vacant buildings as a common good to serve the community, Communa is able to communicate, influence, and sometimes foreshadow the usage of a space towards more social impact and community needs on an immediate (e.g. emergency shelter for homeless) or longer-term basis.

For example, by collaborating with a local community of senior and young residents, Communa convinced a private owner of a vacant residential building who had planned to create an intergenerational café within the building that this would not have the wished upon effect: the experimentation phase had shown that, although it did appeal to young people, the idea did not attract elderly people at all. Communa tested other inclusive methods in the empty building such as a shared community fridge and library, both of which led to more intergenerational interaction, which are now being implemented in the reconstruction of the residential building. This way, they are turning temporary use into a transitory urbanism tool able to influence the future usage of an unused, empty building as well as inspire the way the city is designed, creating a counter model to the current top-down market logic.

As an outcome of their activities, they have already worked on more than 20 buildings that provided housing for more than 200 people and allowed more than 250 social and neighborhood organizations to start their activities, with many consequently moving into permanent spaces in the neighborhoods. Communa also managed to influence property owners to pivot the initially designed purpose of their vacant buildings, by involving the community in designing a new purpose that would provide housing for refugees, homeless and create spaces for intergenerational living.

Being aware of the sheer size of opportunities provided by vacant spaces to transform the cities and willing to spread their knowledge to a maximum of other actors, Maxime and Sâm are increasingly sharing their tools in an open-source manner. The tools are based on meticulous documentation on the processes of how to deal with property owners, how to create the technical and legal frameworks in which temporary use can happen, and how to build and maintain self-governing communities within their spaces.

Through this they aim to professionalize an uncoordinated sector and thus facilitate its systemic impact on urban practices.

For the Belgian sector, Communa is collaborating with the renowned Academy of Fine Arts in Brussels, to create a master’s degree in Temporary Use. Through this, they will be teaching a fully new profession of the “Temporary Use Expert” who will learn, in a university environment, about Communa’s tools and legal frameworks. Additionally, the students will, through internships, be immersed in temporary use projects for practical exercise.

On a European level, they are currently building a robust training program and toolbox with the legal, administrative, and community aspects of transitory urbanism, funded and supported by the European Union. This European dimension has been possible thanks to the creation of the Social Temporary Use Network (STUN) which Sâm and Maxime strategically initiated in collaboration with temporary use actors from eight different countries in Europe in 2019 (which includes French Ashoka Fellow Nicolas Détrie, founder of “Yes We Camp”). Through STUN, Sâm and Maxime are building the European network to exchange knowledge and best practices, as well as to give credibility and influence on temporary occupation, as STUN’s aim is to act as an international body, similar to an official observatory.

Besides the bottom-up empowerment and professionalization of the sector, Maxime and Sâm are convinced that institutionalization and regulation are key as the third axis. For this reason, they have become very active in advocacy activities to anchor the establishment of TUSP as an actual new norm and not just a trend. Through making the social purpose of temporary occupation legally binding in public tenders they want to make sure that the trendy concept of temporary use is not skewed by for-profit practices increasingly observable through pop-up shop, bars etc. They lead creative lobbying efforts in partnership with other actors of the sector to make it institutionally recognized and defined.

To be legitimate and heard by institutions and decision-makers, they understood that they had to raise awareness and aim for public visibility to convince decision makers to adopt new practices. An iconic example of their action is the creative campaign they launched during the elections in 2019, putting a new 20th district of Brussels (Brussels has only 19 physical districts) on the map they had coined “Saint Vide” (literally meaning “Saint Empty”). This new district was based on their realization and data collection that in Brussels the sheer size of 6,500,000 million square meters of vacant space was available, making it theoretically the 9th largest district of the city that could provide housing to 30,000 people. To turn this theoretical district into action, they built a website of the municipality for people to get informed about the issue of vacancy, put stickers and posters on the most visible and known empty buildings in Brussels and led several TV and newspaper stories to spread awareness of the problem and their solution of TUSP. The success of the campaign contributed to making the housing crisis a very politicized topic during the late 2019 regional elections. As they cleverly promoted temporary use as a best practice, they managed to get the newly elected government to include the definition of TUSP in the coalition treaty part of the region’s urban and social planning policies to overcome the housing crises.

Building on this major victory, they are now working on creating a legislative framework to ensure that empty buildings are put into the service of the community and are blocked from any commercial usage. For this they are propagating the notion of Temporary Use with a Social Purpose through different ways: Firstly, by disseminating TUSP through a consultancy approach they have developed for pioneering municipalities. They are increasingly consulted by municipalities to support them from A to Z in their reflections of creating temporary use projects and in writing the necessary public tenders for other social organizations to do temporary use projects. Knowing that supporting the pioneers will systematically engender an imitation phenomenon by other municipalities, they can now observe public tenders coming on the market from non-accompanied municipalities that include elements of their language already and demanding temporary use with a social purpose for empty buildings. Secondly, they are working on deepening their impact on legislation through a collaboration with a law firm to find ways to make Temporary Use with a Social Purpose mandatory for private and public actors when doing temporary use projects. Lastly, through being an outspoken and recognized authority in the field they continue doing advocacy work by being invited to public hearings to further develop this notion in the public discourse.

Eventually, they are exploring how alternative forms of property ownership can enable the creation of new vehicles that could take property out of the speculative market and allow citizens to build a more inclusive city. For example, through social ownership models and forms of land ownership for social impact, they aim to accelerate the urban transition to more democratic spaces by fighting the disconnect between property ownership, citizens, and a building’s usage. In this same line, they recently launched “Fair Ground,” a partnership with a real estate cooperative project, the Community Land Trust (the Belgian antenna of a British Ashoka Fellow’s organization) and other social organizations. Together, they will acquire vacant property in Brussels and incorporate it into a community land trust and create temporary occupation projects in these buildings. As they will be the owners of the space, their “temporary use” model turns into a “permanent temporary use” adopted to the needs of the communities living on and using the land. This would enable urban spaces to shift easier depending on the needs of the community without needing to convince the owners.

The Person

HHaving grown up as an only child in a multicultural family, Sâm has always been very sensitive to the notion of community and transition. He was raised as a nomad with divorced parents, spending his childhood carrying a suitcase moving back and forth between the respective homes of his father, his mother, other family members, and his friends. By the time he was 18, he had already moved 13 times within Belgium.

The one constant element that remained was the community experiences he lived through, his participation in a Jewish Youth organization (equivalent to the scout movement) in which he was active every Saturday and every vacation to his late teenage years. Being a youth leader at the end, he was also elected to represent the organization externally in annual gatherings on a Belgian national level, where he could collect his first leadership and advocacy experiences. Through his multicultural roots, Sâm became at a very early age familiar with the notion of inherent conflicts and the tensions that arise from them. A desire thus grew in him to learn about how to overcome the tensions and reasons that create them causing painful break-ups.

With these conflicts and reflections in mind, Sâm decided to study law as a powerful vehicle to bring change. Although he found himself very bored by the content, he excelled as a student. Having a passion for listening to and hosting radio shows, he spent a big part of his student time in creating his own radio shows leveraging on the technological resources provided by the university, where he could discuss political topics and invite inspiring people to discuss about the themes that mattered to him such as alternative forms of co-habitation. To host the shows he got involved in the leadership of the Jewish student union at university, together with Maxime, the co-founder of Communa. Also after graduating from Uni, Sâm continued, with a group of volunteers, to host a daily radio show.

During the second part of his studies, Sâm became increasingly engaged in the subject of temporary use, as he and a group of fellow students, amongst which Maxime, were looking to find a space to create a co-habitation project with the aim of re-creating the collective spirit he experienced during his youth days. Not being able to find affordable spaces to rent and being aware of some squats in Brussels, that Maxime had introduced him to, he analyzed the "squatting principles" and combined it with his knowledge from law school to learn more about temporary occupancy agreements and the legal possibility of living in vacant buildings. Having found a way of legally occupying a building without having to pay rent, Sâm and the rest of the group approached private and public (municipalities, region, university) owners to inquire if some of their buildings were left unoccupied. Together with Maxime, they convinced the university about the legal and social concept they had developed to use buildings for housing and social projects and got connected to the owner of a vacant office building of the size of 8000 square meters whose owner accepted to provide the space for their project.

Being empowered through this first success and realizing how he could apply law in a very practical way that was close to his interests, Sâm continued to investigate the legal and structural aspects that accompany questions around who has the right to the city. As the leader of Communa’s collaboration with local municipalities to empower them to apply the TUSP model, as well as Communa’s lobbying efforts on a federal level for the adaption of TUSP in all public tenders, Sâm is continuing to leverage on his experience and legal knowledge ever since for example in the creation process of Fair Ground, in which he is representing Communa as a board member.

Are you a Fellow? Use the Fellow Directory!

This will help you quickly discover and know how best to connect with the other Ashoka Fellows.