Pack Rat.....welcome to Garage Journal. If you would, could you put N.W. Ohio into your profile? It makes answering questions like that a lot easier.
Landlord30....ditto to you. Welcome to Garage Journal.
I swear, I think a third of the people or Garage Journal live in northern Ohio and Pennsylvania. Now wonder our winters are getting rougher, you guys are tipping the state up your way.
Pack Rat......when it comes to a slab, or comes to a full foundation, you can do either. I am getting ready to add a bumpout on one side of my garage, and also an addition on front which will be a 28'x30' addition and a 7' x 24' bumpout.
My current garage has a full foundation. I've built a couple garages on a slab, and I don't like doing it that way all for the fact that if you ever want to wash your garage out, you have water against wood that will wick up. And if you have drywall, you will have dampness wicking in the paper from the backside. Up on a foundation, you can have drywall if you want, baseboard if you want, and won't have to worry about water wicking up.
My bumpout and addition, I am going with a foundation down to the frostline. For us, the frostline is 36", for you I think it may be 42", but not sure.
Also, look into scissor trusses. If you can go 15' to the peak, a scissor truss gives you something like 13'. You say that you don't need a lift, but things like that could change. What started out with a torn rotator cuff in my left shoulder turned into 10 operations and no shoulder left at all. Also with a bad back, and now a blown out knee, I can't get under a car and do anything. So I'm going to get a 4 post lift with casters. That way in the new addition, I'll be able to slide it to the middle and get under most vehicles except my truck, but even I could get under it if I was on a rolling seat. So it's always something to consider.
And like you, we have a 2 car garage on the house, and I built my garage in '99. Sadly, I built what I could afford back then and built it myself. from then until now, I have managed to run out of room, hence the reason for some more room.
So seriously consider what you will be doing in your new space, and also consider what you MAY be doing in the future. A few years back, I didn't think I would have two mills, a lathe, and a surface grinder in my garage, along with 3 rolling toolboxes, stomp shear, table saw, plus other toys to play with. So you need to look a little into the future. After you first retire, you have time to catch up on certain things, and just like now, you find that you are needing a little bit more space. But in a few years, you will have another larger project. Go through the Gallery and look at different garages, compare yourself to what some of those garages hold, and plan your wisely. Nothing wrong with starting a folder on the desktop of your computer and start saving pictures. Keep a notebook beside the computer and take notes of what you want.
Also......be prepared for sticker shock. I used to do all of my own construction. I can't do that now. It scared the **** out of me when I saw the quote for mine, but we decided to refinance since the house is almost paid off. Back in '99, I built a 28'x36' with 6' overhangs on the front and side, insulated and drywalled, full foundation for a tick over $13,000. Now, a foundation and floor for a 7'x24' bumpout is $1800, and I build the bumpout. The 28'x30' addition with full foundation and 5" concrete, plus a new roof over the entire garage, and new siding on the entire garage is $37,500. And that is no finishing anything on the inside. So be a little bit prepared ahead of time for what you will find out as far as price. And good luck on finding a contractor. If it's anything like around my area, you won't find many that is willing to work. But at least being up that way, you may have quite a few Amish willing to work and give you a decent price.
Good luck, and be sure to post up any pics of the project. We do like pics.
Now I'm disappointed. I'm on a city lot and because of setback requirements and the location of my sewer line I can't build a workshop that I already thought was small. REALITY *****!!!