Every construction project regardless of level of complexity should have a conceptualization or design.
In design practice, there are significant differences between the preliminary design and the main design. The preliminary design defines the size of the future object, the position of the object and the orientation on the building plot.
In the main design the preliminary design is further developed and the construction works are executed in accordance with the main design. Main design includes all engineering professions and it meets all necessary standards and requirements for construction.
Complex buildings sometimes require a detailed design in which all necessary construction details are precisely solved and it prevents contractors' improvisations and possible "creative" interventions.