This building challenges the way in which building structure, circulation, enclosure, and lighting produces dwelling space. The program consists of two separate units for basic inhabitation, sleeping, eating, and hygiene, while providing adequate access to ventilation, daylighting, and shelter. The siting of the project tests the human relationship to space and light on a site that is constrained to 12 feet wide, with daylight exposure only on the roof and the East and West facades. Furthermore, the building is required to hover at least 10 feet to allow for pedestrian access below at the existing alley passage. This proposal utilizes the vertical circulation as a light-well to maximize natural daylight throughout both dwellings. Thus, the stairs are working double-duty to circulate both light and occupants through the building. The stairwell is pushed to the northern parti-wall to capture the light that passes over the adjacent building from the south, and allows the downward passage of light through the spindly design and open risers. Additionally, the spatial relationship of the two units is expressed on both the East and West facades, where the thickness of the ‘S’ loop delineates ownership. However, the loop alternates between the two sides to allow for each unit to utilize the entire footprint of the narrow building. This provides for variance of light from the two limited facades and also maximizes livable space within existing constraints. The units themselves are organized by function — the first level of each duplex is dedicated to public use, elevating the bedrooms to the second level.