In this paper I propose a theory of architectural use value. This theory is based on a conception of meaning. By meaning we should not understand a cultural signified that a builder would intentionally encode. We should understand meaning rather as significance within an ongoing use process. In our involvement with buildings a dialectic takes place between that which the building shapes, offers and limits on the one hand, and on the other hand, what we who use the building come to invest in it. We do that through various mental activities, which appropriate the built space. Between imposition and appropriation the built space acquires what I propose to call 'semiotic use value'. This is not a pragmatic value determined by ostensible function, but an incrementally growing value of the building as it exists in history. Semiotic use value is determined along the two axes of differentiation and temporality: buildings, walls, doors establish difference in space – and we in our movements through space negotiate those differences. Differentiation also enables buildings to organise a social temporality. By separating certain spaces from others, buildings create the possibility of social coexistence centered around generic activities. These activities are not necessarily stipulated or culturally articulated. There can be a foreground activity and an attendant activity, which is equally significant, typically that would be: making friends, flirting, maintaining conventional relationships, in short all manners of connecting activities, which the built space can facilitate. I will further emphasise that the social significance of built space is not reducible to hierarchy, or ideological purpose, in the manner theorised by Henri Lefevre. Built space produces micro-social conditions of interaction and temporal organisation, which are then, subsequently, invested with meaning through our mental appropriations. Semiotic use value is the outcome of this process. I will illustrate this theory with phenomenological descriptions of public buildings and spaces: the Oslo town hall, Berlin Alexander Platz, the old Sorbonne building.