Is there a place in Poincaré’s philosophy for common space, that is the space which corresponds to non mathematical spatial notions ? The aim of this article is to show that a positive answer can be given to that question. In at least two texts, Poincaré speaks about a «rough space» which must be distinguished from sensible space and from geometrical space. This paper tries to show that such a space corresponds to common space and that it plays a role, sometimes implicit, in the way Poincaré conceives the construction of the mathematical notion of space out of the sensible space : hence the construction of rough space appears as a step in the construction of geometrical space.