I am counting on you to give me the right answer so I can get my husband busy building an addition on our cottage - with a 12' cathedral ceiling. We want to build a 12' wide x 20' long addition. There is a 12' span from peak to eave - 16" centers - and we hope to use steel roofing material instead of shingles. We got an excellent deal on 2" x 6" x 12'lumber from a local place going out of business. Could we use them to build the rafters? Would they be adequate for the load? If not, would overlapping them make them work? If so, how much overlap? I am counting on you!
Answer:
If you settle for a 10' wide room, you'll have a 6.5/10 slope. In other words, the roof will rise 6.5 feet in 10 and I would not dare use 2X6 on anything shallower than that. I would also still insist on metal roofing and even with the vaulted ceiling, I'd want three rows of evenly spaced cross bridging. On the other hand, you have to take into consideration that I am not a professional and as a DIY-er, I tend to over build. An architect would probably do some calculations and shoot all kinds of holes in my plan.
