I had 15 mil vapor barrier installed. Well worth the few hundred for the big roll of yellow plastic! That area is definitely damp including all the water that comes off a 30x40 roof. Might want to add gutters someday work

There is also rebar throughout, not just near the feet of the lift... I want to drive anything and everything in there that'll fit through the door, including my friend's backhoe, without worrying if the slab is strong enough. It's a minimum of 6" 4000 psi mix. That should be sufficient up

On the subject of polishing, if you wax the floor how do you keep gas, oil, solvents from dissolving the wax? shruggy