Question: how many square feet does a roll of felt cover?
Answer: Roofing comes in rolls 3 feet wide and 36 feet long, for a coverage of about 1 square. When installing roofing over bare wood, roofing felt -- often called tar paper -- is laid down first. A roll of 15-pound felt covers about 4 squares; a roll of thicker 30-pound felt covers 2 squares.