Architectural historian Wouter van Elburg researched the space behind Dutch front doors: the entrance. His thought was that this space plays a role in how a house is otherwise arranged. Based on 2,500 floor plans of houses between 1550 and 1950, he identified eight different entrance spaces. For the research, he looked at the Hendrick de Keyser Association's collection of houses and, for the sake of representativeness, at house floor plans available from the National Cultural Heritage Agency (RCE). National monuments, but also a large number of demolished buildings. Eight variants were identified: the entrance space with ancillary functions (such as houses where you enter the living room or kitchen), the draft porch, the vestibule, the corridor, the transverse corridor, the hallway and the stairwell entrance. Typological floor plan research on rooms (so-called "room types") offers a deepening and complement to existing insights on constructions, materials and house types of historic Dutch residential houses. The study of floor plans, with an emphasis on the appearance of individual spaces, is a new area of research in architectural history.