This chapter deals with the structural design of a power house. Power house is a structure which houses the generating units and provides space for other associated equipment and facilities. The layout of power house is described in detail in Chapter-4. The layout depends on the type of coupling of turbine and generator and the type of turbine. The structure becomes complex when a reaction turbine is vertically coupled with generator because it needs a scroll case as well as a draft tube of specific shape. These are encased in concrete and form the intermediate structure and sub structure of the power house. A superstructure which is made of columns (called gantry columns), beams, roof and panel walls is also provided in an indoor power house. Such a power house is a RCC structure. A design procedure of such a power house based on 2-D analysis is described. Superstructure is analysed as a multistorey frame and intermediate structure encasing the scroll case and supporting generator load is designed as RCC structure by breaking it into simple structural units. Substructure which encases draft tube is designed as a continuous footing. In a horizontal setting power house, there is normally a superstructure and a substructure supporting the turbine and generator at separate locations. This chapter also contains some important findings when both the intermediate and substructure are together designed as a 3-D structure using FEM technique.