This is deep in some technical weeds, but a client asked me to define the floating slab on grade in a two-story building as either a "flooring" or a "foundation" (this matters due to some leasing agreements). I can see two arguments - (1) the primary building structure loads are transmitted through columns, piers, and isolated foundations, and the "building" so to speak doesn't really care if the slab on grade is there or not, so the slab on grade is really the "flooring" in the first floor - or - (2) the loading in the first floor space (retail live load, etc) is transmitted through the slab on grade to the subbase and native soil below, so therefore the slab on grade is a foundation element. Has anyone ever been asked to differentiate? I cannot seem to find a definition of "foundation" in the IBC - other thoughts on where to look? I need some ground to stand on one way or the other - though quite frankly right now, response is "I don't know".