Paris-based architect Jacques Moussafir laughed and then had to count out loud when asked exactly how many floors exist in the 1,650-square-foot house he designed for a bachelor in the city's fashionable Latin Quarter. By Moussafir's calculation, there are 10, including a roof terrace; each level is a single room (if that) branching out from a central staircase core, “like a propeller.” The client requested that there be no doors, and Moussafir's eponymous firm happily complied–though it did enclose two bathrooms. “It's always a dream when a client says they don't want any partitions,” says the architect. Locust-wood paneling on the floors, ceilings, and stairs contrasts with whitewashed masonry walls.

The steel-and-concrete structure sits between two buildings in a residential courtyard, where an old house was razed for the new one. Local preservation regulations dictated that the architect save two walls of the original house. Electronically operated metal shutters with a laser-cut leaf pattern shade the new, glazed southern facade and provide privacy for the occupant–as well as the neighbors.