Heya. For my next build, I'm planning some living space under a garage. Given a 4.5" concrete slab, would you lean towards standard 3/4 OSB sheathing (floor trusses 24"oc), or upgrade it to 1 1/8? The thicker is obviously stronger, but I'm thinking that as soon as the concrete cures, the floor sheathing will all be but needless. What do you think? thanks, brian

Use prestressed concrete like a parking garage... Cheap and they will do all the engineering.

Note, we have prestressed concrete and with a garage below and we get water from the top garage to the bottom. Not bad or a worry for us but is it were living space it would be a big problem.