I am building a 24 by 30 cottage with 2 x 4 exterior walls, 8' high. I want to have a clerestory style roof with the front 1/2 of the house having a roof pitch of 3/12, and the back roof 6/12, which will leave space for clerestory windows facing the front. How should I construct the center wall, which will be holding both roofs? It will be 14' high in total. Can I build this wall with 2 x 4 or should I use 2 x 6? Can I build a 10' wall first, topped with 2 2x12's to support an opening of 12' in the wall, and then put an additional 3' high section on top to complete the height for my tallest roof?
There are of course lots of ways to accomplish this. Since the ends of the rafters from both roofs (rooves?) need support, at different levels, it's a bit of a challenge.
It would be easy to construct the center load bearing wall with balloon framing methods. (Actually the whole structure is very well suited to balloon framing.) However since balloon framing is seldom used these days, not many people know how to do it, and it can be difficult to get permits / approvals etc. But it's very well suited to multi level challenges like this.
The picture below shows a pretty straightforward way to frame it with familiar, standard platform framing. If you look closely you can see that there are really two built up columns in the center. Inside, you could have a double wall - one side built to support the front roof, one side built to support the back roof. That is probably the simplest, most straightforward way to go.
If you wanted the interior wide open, you could also have the built up columns supporting beams, one to support the front roof and one to support the back roof. The beams would have to be carefully sized to support the roof load across the span, and buying / building them and getting them in place would be a big job.
You might benefit from Sean's Shed.