My shop has been in the basement for over 20 years. It started in the garage, but even though it's heated and insulated it took an hour to recover the temperature drop every time a door was opened in the winter. Adding to that the machines would sweat profusely in the spring when the air temperature was warmer than the machines. I finally decided it was time to move everything inside where it could be used daily throughout the year.
In my case the only entrance to the basement is in the middle of the house. You have to go up 1 step from the garage to the kitchen. Through the kitchen (with an island on one side and the refrigerator on the other), through the dinette and into the family room. Then take a right turn to the stairs. There is a wall 4" away at the bottom of the staircase so another right-angle turn is necessary at that point.
Like others (including Johnny Cash) I took the machines apart and "one piece at a time" my assistant and I took them through the house, down the stairs and reassembled them. The larger machines like the Bridgeport mill, Sanford surface grinder, 25-ton hydraulic press, Sheldon lathe, Seneca Falls lathe, US Machine Tools horizontal mill, Jet drill press, and Racine power hacksaw were disassembled in the garage. Some of the smaller machines like the Startrite bandsaw, Delta/Rockwell belt/ disk sander, Black Diamond drill grinder, Greenerd Arbor press, Challenge 24x 36 cast iron surface plate, and the AMMCO shaper went down in one piece.
I did all the disassembly and reassembly and moved all but 2 pieces of the disassembled machines to the basement by myself. The 2 pieces that required help were the column of the Bridgeport (1,000 lbs.) and the motor/drive cabinet of the Sheldon lathe (800 lbs.). The only reason I hired a company to move them was the fact that I didn't have a stair climber dolly big enough to handle the weight, there were no rental units big enough to handle the job and purchasing one would have cost 4 times more than having it done.
Here's a picture of my assistant at the bottom of the stairs waiting to go back for another load of parts: