I have just had a fire at the shop I have rented for over 20 years and am in the planning stage of a shop attached to my home. I have been a carpenter wood worker cabinet maker for nearly 45 years and a back yard mechanic for longer than that. At this point I am considering an over under situation mechanics below with 12' ceilings and woodworking shop above. I am well aware of the space I need for the wood working area but undecided on the footage needed for the mechanics shop. What I am thinking is 24' x 32' x 12' for the work area which will contain a lift as well as all other basic tools. auto storage will be in a another building. So my ultimate question is given a 24' width building what depth would you go?
If you have the room to make the building longer, I would consider having everything on the ground floor- adding space above a 12' (13 when you add the floor) bay may very well exceed Town Ordinances as they pertain to building height. Install radiant heat in the concrete floor, over 4" of rigid insulation. Insulate the hell out of the building.
I like the over / under idea of segregating the wood working and mechanics. As for the depth of the mechanics area, I'd suggest you do a layout using graph paper. A crew cab long bed truck is very long... vs. a 1951 Chevy pickup. So what you anticipate working on will drive the dimensions. My 1st two shops were 24 ft deep x 32 feet wide and that worked out well but was pretty tight trying to get around in front or behind the vehicles. My current shop is 30 foot deep x 44 feet wide. It has a 2 post lift. I wouldn't suggest anything less than 30 feet in depth for the bay were the 2 post lift will be. This gives you room in front of the lift for a workbench, and still have room to walk all around the vehicle that is on the lift. What I did to segregate activities was built a storage area for the cars, a storage area for tools, and a maintenance bay. The 3 different areas are walled off from one another, with doors and windows meant for exterior areas. All the tools are on casters so they can be rolled into the maintenance bay. More information can be found in my build thread link below. Might not be what you are after, but I just wanted to share, as food for thought on your building.
I think your dimensions are spot on and particularly like the 32 deep. Having a 30" wide bench across the front with storage underneath is handy to both sides for access and still leaves room for floor jack handle or even an air jack front or rear. I tend to line the side walls with various things till passage gets restricted but not everyone is a dedicated pack rat. I have a Rotary 9000# post lift and a 12,000# drive on lift. As I get older I favor the drive on lift which also has the rolling jack(s) option so either end can be lifted for brake/bearing/axle, etc type work. We have enough height to raise it up out of the way when not in use (almost never). I wish I had been smart like the guy at the chop and drop shop near me and made a recess in the floor to put the runners at floor level and do away with the ramps. Monday morning quarterback has a perfect game I guess. Converted all lights to LED's recently and the only regret is I didn't do it sooner. Have been in shops with radiant floor heating and that system is great but probably not worth the expense in Texas. If my shop looked like Lakeroadster's I'd be scouting ebay for an operating table.
No kidding... Mine gets a purge, about once a year. Then three weeks later, it looks just like before. Steve.
Thanks for all the replies. I have decided on adding 32' to my existing 24'x26' garage making it 24'x58' with the new area having a 13' ceiling with the wood shop below with only an 8' ceiling height. I have consulted a structural engineer and he is designing a steel beam floor system capable of carrying a 12,000 lb lift. This system is much like building a bridge for city traffic but should be much cheaper than the 12' lower level garage. Permits are not expected to be approved until fall so I'll let you know how it goes.