I put a 2nd floor in my 12x12 Tuffshed for an exercise room. I put in an AC and a barracks size fridge. It will be getting cable hooked up to a wall-mount flatscreen TV next. It isn't huge, but it fits my bike and total gym just fine.
I'm 5'11" by the way, and I don't think someone much taller could get away with it. It's JUST tall enough for me using reinforced 2x6 floor joists.
I'm digging it!
http://i161.photobucket.com/albums/t...erciseroom.jpg
Threaded Mode
