How do local authorities of small periurban towns come to adopt a national housing policy in order to influence their environment foundation and the population—be it in favor of homeownership or social integration? Based on the study of a growing residential community outside of Lyon known to have voted left since 1983, the article tackles the question of diversity policies, one that is rarely posed when discussing this type of periurban settlement. Our analysis on the sociopolitical and institutional logic underlying the construction of housing developments reveals an ambiguity: the larger “American-style” residences aim to attract middle-class families from urban areas, while affordable housing meets the needs of the local modest households. Nevertheless, local policies are strongly influenced by real estate developers, especially in periods of economic crisis. The statistical analysis of population settlements reveals the gap between the political project of social diversity and its actual implementation, and further illustrates the appearance of ethno-racial and socioeconomic micro-segregation in residential zones.