Marseilles’ central districts, where a number of working-class neighbourhoods persist, are grappling with multiple dynamics. Analysis of socio-spatial evolutions in these neighbourhoods show « simultaneous processes of gentrification and impoverishment » (Baby-Collin and Bouillon, 2017). The private housing stock which is predominant in this area, is faced with major deterioration issues, it is also subject to transformations as new investment strategies emerge. Drawing from a thesis low-end of rental market dynamics in Marseille’s central neighbourhoods (2018-2024), prolonged by a collective research project on the adaptation of the historic housing stock to climate change (Sustherit - 2024-2027), this intervention aims to examine the interplay between spatial transformations and how local stakeholders value ordinary urban heritage. The presentation is based on a qualitative survey of landlords, real estate agents and local public players, as well as an on an in-depth analysis of local urban projects and planning documents.

The paper will first focus on investment strategies in low-end segments of the private rental market, to show how several forms of rent extraction may co-exist in these neighbourhoods. Perception of urban heritage is one element which can shape private player’s investment strategies, especially in gentrifying neighbourhoods.

The second part of the paper will look at the role of public authorities. Since 2018 and the collapse of two buildings in the Noailles district, run-down housing has been back on the public agenda in the historic center. Prioritization of security issues has sometimes led to demolitions, but public action is steered towards retrofitting the historic housing stock. Renovations rely on, a public development company of national interest (SPLA-IN), which aims to provide an exemplary retrofitting model with careful consideration to environmental quality and heritage preservations. Costly for public authorities, this model cannot be replicated indefinitely. Outside of this scope of action, ordinary heritage is sometimes threatened of demolition when local authorities prioritize densification, real estate developments or transport infrastructure. This analysis will allow us to question which heritage is recognized and how public players' interest in ordinary heritage is also linked to spatial transformations.

The transformation of historic housing stock through private investments, developer-led interventions, and individual renovations presents a complex challenge to urban heritage preservation. As historic housing increasingly becomes an asset within global real estate markets, the traditional balance between preservation policies, local governance, and market dynamics is shifting. This is particularly evident in non-listed ordinary heritage—residential buildings that are culturally significant but lack formal heritage protection—where multiple actors play an increasingly dominant role in shaping transformation processes. In response to these challenges, new frameworks that integrate decarbonization strategies with heritage-sensitive renovation are necessary to address the socio-political, economic, and
environmental tensions emerging from these interventions.

This contribution presents the DeCO2 project, an EU-funded initiative aimed at developing dynamic decarbonization pathways for sustainable renovation in the built environment. The project’s social innovation as a Living Lab approach is exemplified at Terrassenhaussiedlung in Graz, Austria, a modernist housing estate that represents an important yet unofficially recognized segment of ordinary heritage. Here, participatory co-design processes engage residents, policymakers, and technical experts in developing energy-efficient renovations while preserving the estate’s architectural and social character. The approach integrates technological innovations such as energy monitoring systems and circular material use with social and policy-driven mechanisms that accommodate resident-led initiatives, investments, and regulatory flexibility. This contribution critically examines how community-driven, scalable, and transferable renovation strategies can reconcile the tensions between
sustainability goals, local identity, and the evolving dynamics of historic housing markets. It reflects on how market-driven transformations intersect with ordinary heritage conservation, highlighting the potential of the Living Lab methodology to mediate between economic pressures and cultural continuity. Through empirical insights from Terrassenhaussiedlung, this study contributes to the broader debate on heritage transformation, socio-technical innovation, and urban policy, offering a model for integrating preservation and sustainability in the evolving governance of historic residential environments.

The founder´s period, or the Gründerzeit (GHS) has been a period of historical significance in Vienna and Budapest, both formerly part of the Austro-Hungarian Monarchy. The area of both metropolises grew due to city expansions beyond the Medieval walls, accompanied by river regulation (Vadas, 2005a; Vadas 2005b), and other large-scale infrastructure projects (Csendes, 2005a; Csendes, 2005b; Hárs et. al., 2016), as well as residential development (Körner, 2010; Psenner, 2023). This resulted in a building stock with many comparable features, such as the Historicism architectural style, the organization in blocks with perimeter construction and inner courtyards, placed in regular grid street structures and many other aspects (Melinz & Zimmermann, 1966; Lélek, 2019; Psenner, 2023). The historical buildings stock is still represented in both cities, shaping their urban landscapes both in a physical form (Vienna 20%, Budapest 16% built before 1919) and as representation of cultural values (Hárs et. al., 2016; Peer & Psenner, 2024). However, recent socio-political processes originating from different political systems and regimes of the 20th century have affected these buildings. In Budapest, the process of privatisation has become a strong driving force behind transformation after the system change in 1989 and led to a high proportion of private and low proportion of municipal dwelling ownership (Cséfalvay & Rohn, 1992; Lichtenberger 1994). Although the ownership structure has also been changing in Vienna, it resulted from the circumstances given by legal instruments in a welfare state (Lichtenberger, 1990). The legal conversion (“Parifizierung”) of tenement buildings shifted individual or shared building ownership to the ownership of dwellings and the proportional shares of common areas according to federal state-wide regulations1. As local and international financial institutions started to see investment opportunities in this historical housing after the year 2000, their intervention through commodification have started to shape this historical building stock in favourable locations, either by demolition and new construction, or by rooftop extension and renovation (Musil et. al., 2021). In our research project TransHerit, one of the scopes of the research is to investigate and compare how financialization processes, housing regulation and preservation, as well as market dynamic of GHS in Vienna and Budapest have transformed the tangible preservation of this historic housing stock. In the scope of this session, we would like to present our preliminary findings and shed light on what this could mean in term of heritage regime.

The reuse of buildings offers substantial environmental, economic, and social benefits, presenting a sustainable alternative to new construction and urban sprawl. However, the multidisciplinary nature of building reuse, especially in historic residential buildings, involves diverse stakeholders with often conflicting interests, such as heritage preservation, financial viability, and environmental efficiency. These complexities pose significant challenges.

This study aims to identify and classify the challenges associated with the reuse of residential buildings from a multidisciplinary perspective. It also explores the relationships between these challenges and their occurrence at various scales, addressing the core research question: What are the key challenges and conflicts of interest that hinder decision-making in the reuse of residential buildings?

Through a semi-systematic literature review combined with thematic analysis, the study identifies 75 sub-challenges categorized into 10 overarching themes: : (1) economic viability and financial challenges, (2) building conditions, (3) design-technical challenges, (4) location challenges, (5) decision making, (6) policy and regulations, (7) knowledge, capacity, and skills, (8) culture, perception, and awareness, (9) surrounding community, and (10) timeline. The findings highlight strong interconnections among these themes, with financial viability emerging as a critical influence on many other aspects.

Existing research on building reuse often adopts a narrow disciplinary focus, lacks a holistic multidisciplinary perspective, and overlooks the interplay between different challenges, particularly in residential buildings. This study addresses these gaps by providing a conceptual framework that categorizes the challenges of residential building reuse across multiple disciplines. By categorizing these challenges, the conceptual framework serves as a resource for policymakers, researchers, and educators in understanding the complexities of building reuse. In addition, it can be utilized to further develop strategies, policies, and decision-support tools to effectively address these challenges.