Matt, I had a Cleary 30x40 building built, 10' or 12' walls. Gable Truss' with a bonus room that is or will be 9'x40' its 5' something high at the edges and 7' in the middle. I love it!
I could have built it bigger but I figured then I'd just fill it with more ~things~
I do not have in floor heat, however if I were to do it again I would!
My upstairs bonus room is currently under construction, I have a floor on 24 of the 40 feet, some day it will be all done. I have a stairway going up there, some day will be on hinges to raise it up out of my way for more floor space, and electric winch lifting it will be the plan. I do have a electric winch on a trolley to lift things up the this upper level, I currently have 5 Cub Cadet motors sitting on a bench up there.
In the back corner I have a 10x14 room that's insulated that I can use in the winter.
In the middle in the back of my shed I have a Dog Door for Coco my Chocolate Lab. This dog door has proved to be handy when someone locked the shed with the keys inside, luckily the dog door was not locked...
I have 2 utility doors one on the front that I use all the time, one on the side of my building. This one comes in handy when I'm in the back yard and need to go into the shed. I have 1 12x10 roll up garage door in the front. I have 4 windows around the building and 1 window on each end up in the peaks, for a total of 6 windows. Both utility doors have windows and there's windows in my roll up garage door - I guess I liked windows at the time I ordered it...I'm guessing the sales guy was happy.
There are many days that I wish it was bigger but some day I'll spend a week cleaning and organizing it and I'll have tons of room.
I know I have a lot of some days...but at least I have a plan.
2 things I would change for next time are the in floor heating for at least a part of it and I'd make the wall taller to fit a 2 post lift, travel trailer, etc...
I do plan to have it cleaned and organized by May 1st