Since 2003, more than 400 popular districts categorized as sensitive urban zones and 4 million inhabitants have become part of a program initiated by the Framework Act on Town Planning and Urban Renewal (so-called “Borloo law”). In order to achieve district transformation and social diversity, the program has led to demolition/rebuilding operations, the refurbishment of existing dwellings and the redefinition of public urban areas (street network and green spaces, etc.)The municipalities of Clichy-Sous-Bois and Montfermeil in the Seine-Saint-Denis region were part of this program. Whilst being the largest program in France (in terms of allocated budget and demolished dwellings), it also had the singularity to involve the destruction of dilapidated privately-owned buildings such as Les Bosquets in Montfermeil and La Forestière in Clichy-sous-Bois. All the new buildings reconstructed there are under social housing management.All re-housed inhabitants consequently moved from the status of owner-occupiers or private housing tenants to that of social housing tenants. In addition to their change in status, this situation implies regular interactions between these ‘displaced’people and the professionals (of the city, of nonprofit organizations, social landlords who operate in the area, in these buildings within the frame of pre- and post-rehousing accompaniment.Based on an analysis supported by interviews, observations and archives, this thesis aims at understanding the genesis of this policy as much as the effects of the will for district transformation through generalizing social housing, on professional practices and the trajectories of the re-housed inhabitants. To this end, archives and interviews help understanding that the degradation of the former co-ownership properties was attributable primarily to their conditions of marketing, construction and management. Yet, all the measures of public action, up to the signature of the urban renewal program, systematically present the inhabitants and their features (popular classes or migrants) as solely responsible for this deterioration.The ethnography of professional practices then shows how in the new homes the professionals use the interactions with the inhabitants to regulate the way they live there. This work is done with a view to avoiding new damage to the buildings.Eventually the interviews with the inhabitants (made before and after re-housing) illustrate how re-housing and the interactions with professionals destabilize them within their individual anchorages and shake the sense of hierarchies within this social group. While former owners made up the upper class in their previous housing, they now feel the most downgraded. Conversely, tenants who were the most dominated are today the most rehabilitated.Beyond empirical results, this analytical approach rates the issues of the thesis on sevral scales. First, this work illustrates how, in a constructivist perspective, these co-ownership properties and their inhabitants have been built as a problem and a category of public action. Then, starting from the practices of professionals, this thesis discloses how within the frame of urban policy, some forms of regulation and domination over certain targeted publics (here working classes and migrants) are still exerted. Finally this thesis is consistent with a sociology of popular classes who are attentive to their internal differences as much as to the various ways a measure of public action can be perceived.