KKZ house A two-floor residence with a basement in the cozy town of Setagaya-ku,Tokyo. It has a half-basement free space which can be a child room in the future, the living, the kitchen, and the dining room in the middle floor, and the private space in the second floor. In spite of its restricted premise, it makes the residence so spacious by connecting these floors with voids which run through the entrance hall and above the kitchen, respectively. Furthermore, the integrated 180mm-thick LVL beams make 6m of a column-less second floor slab possible. With this simultaneous design of the floor and the ceiling by a single slab, though simple it is, one can feel the presence of structural materials.