Jerilynn,

Since you are in the planning stages and I'm not sure how cold it gets in your area...may I suggest heat tubes in the floor before you pour the concrete slab.

My father in law did this and heats it with a 40 gallon water heater. it sure is nice working when the floor is warm and toasty

Caution: Take pictures of the location of the tubes and plan ahead
for things that might be mounted to the floor IE: car lift, Compressor, work benches. You do NOT want to drill holes in the concrete / tubes.

One more suggestion...Lots of electrical outlets!

Oh and go taller than the standard 8' if possible lift is in the future.

Tom