Expert: Bruce E. Johnson - 7/5/2010

Question
QUESTION: I would like to know the weight of a 24'x32' roof structure using 2x6's for rafters and joists, 1/2" osb for decking, and architectural shingles. I am trying to figure the size of I beam I will need to span the 32'.

ANSWER: Hi Steve, How about I provide you with the weights and you do the math? For the shingles figure 3 pounds per square foot of roof area.  For the OSB figure 1 pound per square foot of roof area, for 2x6 figure 2 pounds per lineal foot..your roof area is approximately 1062 sq feet with a  4/12 pitch and a 24" overhang on each end. Each rafter is 12'-7" plus an overhange of 2 feet makes them 14'-7" each x two plus a 24 foot joist equals approximately 53 feet per rafter joist combination..with 24" spacing you will multiply 53' times 17 to get your lineal footage for your roof framing. So I hope this information is what you are looking for..please write again as needed..sincerely bruce e johnson

---------- FOLLOW-UP ----------

QUESTION: Thanks for the help. Just one more question. How do I equate the lineal foot to pounds per square foot?

Answer
Hi again Steve, your pounds per lineal foot on the total weight of the rafters is added to the congregate weight of the the osb and the shingles.  All of that is then divided by the square footage of the building to get your psf..I hope this information is what you are looking for..please write again as needed..sincerely bruce e johnson