Abstract
This study aims to deduct practical method for securing distance between buildings & open spaces of multi-family housings in existing lot conditions. For this we analyzed existing lot conditions by using GIS data of 446,579 lots. And we simulated FAR changes in securing distance between buildings & open Spaces by using mathematical models. Some policy implications of this study can be summarized as follows. First, institutional and economical supports are also needed for gradual improvement of environment of multi-family housings, because existing buildings have much more floor areas than attainable total floor area. Second, differentiated regulations by types of lots are needed, because there are great deference in result of simulation among the types of lots.