You can never have too large of a garage, and I suggest that you build it as large as you can afford, even if that means doing a lot of work yourself, and leaving out some things that can be added later as money allows.. An example would be to frame out for all the garage doors, but not install them immediately. You can put in a false wall in the opening a lot less expensively than buying the door itself. I would also consider going with a 15 or 16 foot ceiling, in case your plans change in the future and you decide that you want to lift something that is higher. The concrete only needs to be 4" thick over a well compacted base. Also, insulate the floor for your comfort in later years. In essence, all that you do not that cannot be done after it is built is what you want to include. If you think that at some time in the future, you will want to add heat, then install the PEX tubing before the concrete is poured. You can always add the furnace at a later date. Same with including access piping for telephone, INTERNET, electric in the basic building. You can always trench and hook up these PVC pipes at a later date. I would think that a 42' long, and 32' wide building will handle most needs for the future. My garage is 28' wide, and 38' long, and it isn't long enough to put both of my Cadillac ambulances end for end. I come up 2' short. Also, remember that the dimensions are always the outside dimensions, so if you use 2" X 6" for building, you will immediately loose 1' of inside space. All this is to be considered before you put the first shovel into the ground. Bigger is always better, and not that much more expense when you do it initially.
