In contrast, the incidence proportion can be calculated as 16 â 2,100 = 7.6 cases per 1,000 population during the four-year period, or an average of 1.9 cases per 1,000 per year (7.6 divided by 4 years).
The Costs. Minimum Cost: Approximately $.50 per square foot. Maximum Cost: Approximately $2 per square foot. The size of roofs vary immensely from a standard, urban roof measuring about 800-square-feet to suburban roofs, which often range above 1,500-square-feet.aximum Cost: Approximately $2 per square foot. The size of roofs vary immensely from a standard, urban roof measuring about 800-square-feet to suburban roofs, which often range above 1,500-square-feet.
Do-it-yourself materials to install an asphalt shingle roof on an average one-story ranch-style home (with a gently sloping roof of 1,700-2,100 square feet) can run $680-$3,700, depending on the quality of the materials.