The urban boundary acquires special characteristics in the confrontation with housing, since the domestic dimensions are particularly suited to assume the changes of scale that contact situations entail. This publication aims to address these issues based on the teaching experiences of the last courses of Housing and City, and the collaboration of some of the guests who have participated over the years. We wanted a project of the void, the usual limit of its relationship, to be a substantial part of the teaching reflection. In short, an attempt regarding the concept of Limit to visualize the complementarity of the residential aspects with the urban ones.