The design of the building is widely based on architectural, engineering and technical documents. All construction projects require the services of a building designer, usually a certified architect or structural engineer. In smaller and simpler projects, a professional person with a degree is usually not needed, and the design of these projects is usually under the hands of a building designer, draftsman or an interior designer and contractor. But larger and more complex projects require the services of many professional and trained people under the supervision of an architect.