There is provided a structure that is a prefabricated (or systems-built) building space including a floor assembly, modular wall assemblies, and a roof assembly. The structure may at any time be connected to one or more other structures or prefabricated room extensions to form integrated building spaces. The structure is attached in a semi-permanent connection to a helical pier foundation assembly. The structure can include a locking mechanism adapted to be removably fastened to the floor assembly and the foundation assembly.