A single staircase of a nine-story residence cannot be converted. According to the relevant public information, after the building is completed, in order to ensure the health and personal safety of residents, the structure of the building, including floors, columns, stairs and other major buildings, cannot be changed, and the single stairs of a nine-story residence cannot be converted. Residential houses refer to houses exclusively for living, including villas, apartments, dormitories for employees' families and collective dormitories, single dormitories for employees and students, etc. , but does not include the basement used for civil air defense and uninhabited in residential buildings, nor does it include nurseries, wards, sanatoriums, hotels and other houses with special purposes.