I know this isn't a cabin build but hope you all will enjoy the pics when it gets underway anyway. My wife and I do have a 30x30 cabin with loft and garage/basement that we've done quite a bit of work to since we purchased it but I'll start a separate thread for those pics when I get them off the camera.
I'm starting with a 20x20 shop with 8' walls and a pyramid roof. I finally got the wife to 'ok' building a 20' wide by 40' deep garage for the boat and gym/guest area in the loft. The current shop has about 4-6" of concrete extending beyond the exterior walls. Between that and the grade, I plan to build stem walls around the existing 20x20 foundation with them extending behind the current shop out to 40' deep. The stem walls will ensure the slightly rising yard slope isn't above the sill plate as well as provide a solid continuous foundation for the entire structure.
Out of the 40' depth, I'll use the front 30' that faces the driveway to install a 12' garage door so that we can store the boat with the wakeboard tower up. The back 10' depth will be finished space with a loft above it. My plan is to build 12' walls using 2x6s and scissor trusses. This will give me enough room to install a 12' door. I'm still not sure how wide I'll go but it will be at least 12'.
Lately, I'm starting to have a few good idea fairy thoughts and realize the walls, trusses, etc. can be done many different ways.
My first thought is to build all four walls 12' high out of 2x6s with scissor trusses on top. For the back 10x20 area, I'll run 2x6x8s to set floor joists on next to the 12' tall studs. This will do a few things...make the walls stiffer, eliminate the need for a ledger, and make floor joist installation quick and easy.
The other option would be to build the front 30' of walls 12' using 2x6x12s and the back 10' using 2x6x8, then double top plate, rim joist/floor joists, and pony walls on top. Using scissor trusses, this shouldn't be an issue but initially is seems like more work.
As far as the roof, I could utilize a ridge beam but the scissor trusses seem like a faster and more manageable option while still giving me enough head room. I should have 42" of wall in the loft before the slope from the trusses. An 8/12 should give me 4/12 inside, yielding another 40" at the center for a total of 6'10". I could go slightly lower for the ceiling/floor to gain some loft space.
Building using all 12' walls would allow me to build the walls quickly, set the scissor trusses on top, and get the whole building closed in, then build the loft anytime.
So, to wrap up, the front 20' wide and 30' of the 40' depth will be boat storage, with a stairway for the loft along the back corner. The last 10' depth will be finished along the whole 20' width with a loft above. All walls will be 12' but I'm undecided on how to build the back 10' of wall. I'm leaning towards using all 12' walls with parallel 8' studs doubled up to hold the floor joists. It seems like the most straight forward option.
From the current building, I won't be able to salvage anything from the pyramid roof but will have plenty of 2x4x8 studs. I'll probably use these to frame out the wall between the garage area and finished area.