Design loading for human occupancies come in in the range of 100psf, which is something like 500kg/m2. That's roughly one 200lb adult per 2sf. You can pack a _

Design loading for human occupancies come in in the range of 100psf, which is something like 500kg/m2. That's roughly one 200lb adult per 2sf. You can pack a _lot_ of humans into a small space. Cars are about half that, because they don't pack well. Of course, libraries are even worse, sometimes you're looking at 300+ psf design loads there.