The outside parameter will be very thick but as for the center of the floor, 4" is fine but if you feel like your ever going to store a backhoe of 18 wheeler then go 6". Ill post a picture of a floating slab garage I did this morning (yes I took a picture of it just to post on here lol)
Well, I'm going to be "storing" a 6500 gallon tank at 52000 pounds of water! I think I will be going with 6" thick Fibermesh

Thanks for the pic
