This study examines the Singapore public housing supplied by Singapore Improvement Trust (SIT) in the 1950s. Focused on the Princess Elizabeth estate and Princess estate of Queenstown, this study surveys their construction backgrounds, site plans, unit plans, architectural designs and meanings. The Princess Elizabeth estate was the model estate for workmen’s flats. This estate showed mixed blocks of flats arranged around a large quadrangled open space for children. The Princess estate was a neighborhood of Queenstown, Singapore’s the first new town. At this Estate, there were some new architectural occurrences departing from the Tiong Bahru Estate. Those are the appearance of high-rise typology, and the increased specificity in the functions of open spaces. Thus the open space became to get hierarchy, and divided an estate to small neighborhood units. For the SIT, open space is synonymous with the improvement of urban environment. Through the purposeful creation of open space, the SIT intended to solve the problem of sanitation and to make a neighborhood unit which can be pleasant place for regional community.