The purpose of this study is to investigate the present status of dwelling spaces and deduct sustainable elements in transformation of them by comparing the restored drawings with the surveyed drawings focused on traditional houses that exist in the urban area of cheongju city in Korea. In alteration and extension of these traditional houses, scale of a private room became larger as it has been connected and expanded, the exterior main hall (Daecheong) became the interior living room, and the conventional kitchen was westernized and changed from K type to DK or LDK type. The toilet located at outside was installed by the attached aisle (Toetgan) inside and the existing room. The extension was completed with equipments, storage space, and rental accommodation. The conservative and sustainable elements in the various transformation of them are as follows. Firstly, it was to maintain 3 rooms such as main room (anbang)-main hall (daecheong)-detached room (gunnunbang). Secondly, it was to sustain the circulation of kitchen and arrangement of the - type worktable even though it was westernized. Thirdly, extension of storage space was completed less than 600 mm within the eaves. Although there were functionally and structurally many changes in 18 houses, 4 houses had maintained wooden floor of main hall, 5 houses long planked wooden floor of the attached aisle, and 12 houses rafter ceiling of the main hall and the attached aisle.