Room or suite of rooms and its annexes, in a permanent building or part of that building which is distinct from a structural point of view concerning the way which it has been built or transformed, is destinated to serve as a dwelling to a private household all the year round and is not at the time of the census used wholly for non-residential purposes. There must be a seperate access to the street, direct or via garden or grounds, or to a common space within the building (staircase, passage, gallery, etc.).