Howdy On My shop I went 40' X 60' X 16', which is really 39' X 59' X 16'. If you are going to put in shelves make sure you plan for that, also I went 16' for motor home parking, lifts and a second floor possible train/office setup. As for the shop construction 3 things Builder carries a Bond (my buddy had to fight in court to get the Contractor to finish), additive to concrete to stop water wicking, and depending where your doors are gutters. I hope that this helps.