In 2014, Chile committed to promoting sustainable cities through a National Urban Development Policy that sought to align itself with the Sustainable Development Goals (sdgs). After 40 years of subsidized social housing policies, applying sustainable urban development is a challenge in cities with considerable rates of socio-spatial inequality. This research aims to analyze coastal cities, focusing on Arica and Coquimbo-La Serena, which, due to their location, have tended to have significant transformations over the past 20 years. We have used data on health services, housing quality, overcrowding, and Urban Development Standards. The results confirm that water has become an important issue in a context of drought in northern Chile. Subsidized social housing, in addition to being vulnerable in the provision of water, has a questionable structural quality in the face of important climatic events, as well as overcrowded conditions that make them more critical in terms of sustainability. It is concluded that the application of sustainability in urban policies of the 21st century can be a harmonious discourse, but the reality of the coastal communes is far from reaching this condition.