Top-down construction is a method used for deep excavation systems. It is different from the conventional bottom-up construction method, in that it requires erecting and constructing floor slabs right after each excavation. The advantages of top-down approach are listed below: The structures above ground can be carried out simultaneously with the structures below ground. This greatly reduces the time for construction. By using this approach, settlement can be reduced. Since the permanent columns and slabs can be utilized to support loadings during construction, it saves the cost of formwork.
