Before we talk materials, let’s talk terminology. Roofers don’t usually use the measure “square feet.” Instead, they talk in squares. A square is their basic unit of measurement—one square is 100 square feet in area, the equivalent of a 10-foot by 10-foot square. The roof of a typical two-story, 2,000-square-foot house with a gable roof will consist of less than 1,500 square feet of roofing area, or about fifteen squares.
A number of considerations will affect the cost of a new roof. The price of the material is the starting point, but other factors also must be considered. One is the condition of the existing roof if you are remodeling a house—if old materials must be stripped off, and if the supporting structure needs repair, that will all cost money. The shape of the roof is another contributing factor. A gable roof with few or no breaks in its planes (like chimneys, vent pipes, or dormers) makes for a simple roofing job. A house with multiple chimneys, intersecting rooflines (the points of intersection are called valleys), turrets, skylights, or other elements will cost significantly more to roof.