Abstract: An automated method and system generates a specification or construction of a building based upon a floor plan, and using modular elements selected from a predetermined set of modular element types. Computer-readable input data representative of a user-generated floor plan is received, which is made up of modular elements arranged in accordance with a regular grid. The input data is processed to produce computer-readable specification data which includes a specification for construction of a building from the modular elements, in accordance with the floor plan. At least one output file is generated, which includes information for use in construction of a building in accordance with the building specification data. The invention enables the design of modular building structures, which can be deployed relatively rapidly and cheaply, by users having no particular skills in building design and/or structural engineering.