I'm just finishing up a 26 deep by 46 long garage built into a bank with 12 foot ceilings and a full upstairs. Total concrete for the project was 100 yards with ten inch walls reinforced wit rebar in the walls and also in the footings as per the new code. We used I Joists that could span 33 feet spaced 19 inches on center, but we spaced them 12 inches on center to eliminate any bounce, and we really have a solid upstairs floor with no bounce. The I Joists are 16 inches tall and laminated nailers top and bottom. we filled them with insulation and ended up with R-51. The garage is totally sheetrocked with 5/8 and that makes the I joists more rigid also. Nice to have clear span to move around in. The garage space never goes below 41 degrees, even with the nights we have had this winter at 10-15 below, so the pipes won't freeze, but I have a 100,000 btu propane modine heater just in case and when we work in there. I used three O/H doors (10X10) with R-16 insulation. I would recommend wider doors as it's tight getting the one ton in with the mirrors. Two 16 foot doors would be the best for me. Feel free to PM me with any questions if I can help.