[chickenwing]

Just went through this. Research out the lift you want. Now determine how wide your bay opening is gonna be. Redetermine what lift you want. Determine what your sidewall height will be. Redetermine what lift you want. Sidewall height needs to be a bit above 12' for a 2 post above ground lift. Determine how deep into building lift will be based upon your longest vehicle. Nice to close a bay door while truck is on the lift. Now ya might can figure out where your max thickness needs to be for your lift. Bendpak specifies only 4" of 3000psi rated crete for their 10000lb 2 post. Why make it all only 4" when you can go a bit thicker on your load bearing areas? Minimal additonal cost that way. I went with fiber no rebar. Pad as a whole is non-load bearing on mine as I have a pole constructed building. So I poured no footing around the perimeter. (If it I did go stick built it would have had a footing. Doubt inspector would allow you to go without one if that is the case.) Did go a bit thick on my primary service bays (6"-8"). Did cut control joints in mine on 10' centers while it was still green. Totally agree with a raised sloped pad, particularly if you reside in a wet climate. Go with a vapor barrier below the concrete too to prevent sweating. Know I didn say a darned thing about rebar but hope I helped.