I take it you don't have an answer?
You will need 30# felt every 8 inches of most cedar shakes. Thirty pound felt gets put between every layer of shingles, with an 8inch exposure every layer. You will need 3 rows for 3 sqs (roll of 30# is 3dtx10ft long) 15% waste on a hipped out roofCan anybody tell me simple way for calculating how much 30 lb. paper is needed for cedar shakes?