A building has a 50′ x 100′ flat roof. The felt is 4′ 4″ wide and 100 ‘ long. How many rolls are needed to cover the roof if there is a 3″ lap?

A building has a 50′ x 100′ flat roof. The felt is 4′ 4″ wide and 100 ‘ long. How many rolls are needed to cover the roof if there is a 3″ lap?