I'd like to add a 3rd story/gambrel roof to my house. I believe that I could do a semi-cathedral ceiling using plywood gusset plates in place of ceiling joists but can I also push the knee bracing (interior walls) outward to give more room space or do they have to meet at the joint where the upper and lower rafters meet? Thanks, Jim B.

Jim, I would suggest to start with a call to your building department and ask what they require for this kind of project. Sometimes you need to employ a strutural engineer to verify thet the foundation and home framing can carry the load.

I built a house for myself once with same situation, and made the knee wall only about 3' tall, but I was able to run beams laterally right under the break in the rafters and run them from bearing wall to bearing wall to carry the loads.

I would have an engineer look at this one.

Good luck

Roger