I put up a 26x30 Carolina Carport, and enclosed it by building my own end walls with PT 4x4s and installing two 10w x 7-3 roll up doors.
My thinking was that there would be enough room (26') in front of my 17 foot long B bodies (and Dakota) for a work bench and me to work, and also to get by in the back.
That worked out pretty well, but another foot would have been nice. 28 sounds good.
At 30 wide, I tought it would be a very generous 2 car, with room to open both doors on both cars, or a tight three car if necessary.
In reality, it's fine for two, but I have packed so many parts shelves, cabinets, tool boxes, sand blast cabinet, compressor, etc in, that it's starting to become difficult to get around, although it's just a matter of carefull placement to open the doors all the way. No way am I gonna get three in there.
I'm glad I went with 10' wide doors, as you have room for the overhang of the fenders if you are still turning when pulling in. My brother just went with 9' doors and it's real tight, and difficult to walk past if the car isn't all the way in or out.
I have 8' walls. Going to 9' or 10' would have made the roll up doors more expensive, and the horizontal brace for the truss more difficult to reach. I am storing 2 full quarter panels, a half panel, a bench seat, a trunk floor, a hood, an exhaust system and several valances and side trims up there.
I'm using a Gray bumper lift, and currently have one of my cars 18" up on 4 stands. I could go up another 2-3 feet. Not going to stand up underneath, but could sit Indian style, and easily move a trans in and out.
...and I have also contemplated pouring a pad next to it and adding on a lean-to.
Can just barely get a decent pitch on the roof.
Just my 2 cents, good luck with your build.
