I want to pour a concrete slab under my garage door. It is 16 feet long, and is now all rock under it. I like to know how deep it should be, and how wide it should be. Also should it have some slope in it, running water is not a problem now. I need to keep animals from digging under it. This is in a building with a rock floor in it, does not have any concrete in it. Also have another door in building, it is 15 feet long and is a slider door. This also need concrete under it also. Am not sure how deep to pour it. Was wondering if 6in is deep enough. Thank you...

5-6 " should be sufficient for most garage floor but you also need wire mesh or rebar.