I am putting in an 8' x 10' porch that is 21 inches above the dirt around it. The minimum concrete delivery around here is 6 yards. Instead of putting in dirt for fill, I was thinking of just getting the six yards, which would just about raise an 8' x 9' surface 21 inches. As opposed to pouring a slab 21" thick, I want to dig a trenches on either side of the porch & throw the dirt from the trenches where the porch is. The trenches would extend below the frost line. All the concrete would be about 8" thick, with rebar 1' on center.
Does this make sense? I was also thinking about covering the surface with 1/2" thick granite tiles 12" square & putting them down with thinset. As long as I seal it, would this work?