Plan means a diagram or a drawing that shows the engineering of a building. It is depiction of the arrangements and formations of rooms or buildings with the help of a diagram before the building is built. It illustrates rooms, corridors, walls, roofs and each and every part of a building to have an idea about what is to be built. The plans are usually drawn by some who is excelled in it like and architect or an engineer. The measurements like length, breadth and height of a building is initially determined and depicted through a plan before a building is constructed. Plans may be floor plan, roof plan, site plan or even a map-like diagram that shows the horizontal cross-section of a building.