The research presents the basis to articulate the assessment and preservation of public housing complexes, taking as an object of study the medium-sized cities of Sanlúcar de Barrameda, Setúbal and Lelystad. These complexes appear due to the generalised housing deficit –by the transfer of population from rural to urban areas– which characterised European cities mainly during the 20th century. This period was a time of large growth of cities and, therefore, one of greater architectural and urban production in recent urban history. However, these are assets that, in most cases, lack general heritage recognition, both by specialists and non-specialists and, consequently, do not have comparable preservation levels to other residential types in large cities. To address this study, Sanlúcar de Barrameda, Setúbal and Lelystad are contextualised within the set of medium-sized cities of the Andalusian, Portuguese and Dutch coast, to which they belong. These cities were also receivers of these migratory processes due to their strategic location within the territorial structure of their region. The research seeks to make a sequential approach that addresses, from the general –the construction of the conceptual, theoretical and legislative frame that conditioned the construction of these urban complexes in Spain, Portugal and the Netherlands– to the particular, the analysis of each social housing complexes features and their resulting in the current case studies’ urban shape. The study concludes with an approach to the evaluation of the degree of recognition and legal protection of these groups in a comparative analysis among these three contexts. From this approach, and together with the singularities of the cases analysed, there will be gathered the main criteria on which to base their assessment and propose a specific protection instrument. ; La investigación aborda las claves a partir de las cuales articular la valoración y protección de los conjuntos de vivienda pública, tomando como objeto de estudio las ciudades ...