Abstract: A method of forming a multi-storey building structure, comprising the steps of erecting a series of vertically oriented support columns (2) in spaced apart relationship to define a generally vertical support structure, and connecting a series of horizontally oriented support beams (5) to the support columns in spaced apart relationship to define a generally horizontal support structure for a floor. Furthermore, releasably attaching a crane carriage assembly (70) to a rail formation (63) attached to the support structure (B), whereby the carriage assembly is adapted securely to traverse the rail, and hoist, position and secure a plurality of prefabricated lightweight structural panels (10), in substantially contiguous side-by-side relationship on the horizontal support structure to form a structural floor.