Exterior of a building often seems to have a very practical and utilitarian purpose — sheltering the interior of the building and the occupants from the natural elements. But that is just a general role assigned to the exterior. As soon as we look into each elements of the exterior of a building such as windows, exterior doors, roof, entrance, balconies, or decks we realize it is impossible to separate the exterior and interior of the building — the shape, form, color, and the very existence of any exterior shell represent the expectations we would have from the interior of a building. For example a window on the exterior of a building represents the coalition which we expect to have light and ventilation in the interior, a canopy placed over an area suggests where we expect to be protected from the elements, a door situated in the exterior of the building is where we expect to exit from the interior. In addition to all these, the exterior of a building is a manifestation of the structural and architectural style we have chosen for the building.