The SHIMODERA-NITTO Improved Dwellings were built by a slum clearance program before World War II. They are the only buildings that still remain. The object of this study is first to place these dwellings as the historically important program in urban planning, and second to analyze the drastic changing of living space by extension, called "DASHIYA". This study made it clear that this dwellings were a model of housing policy in Osaka before the War, and that under the special restriction dwellers extended house for the purpose of improving the small house to adapt to changing of life style.