This paper reports on a project wherein 4 storied basement was demolished and 5 storied basement was reconstructed. The existing basement had been constructed fully on the site. In order to shorten the construction term and reduce the construction cost, the new basement was designed after sufficient research on the demolishing and retaining procedures. After rock auger work on the existing concrete, soil mixing retaining walls were constructed. Concentrically assembled temporary struts were adopted to simplify demolishing work by hydraulic hammer. It took about 19 months from demolishing the 4 storied basement to reconstructing the 5 storied basement.
