I remember reading this story in the 70s. It took place In The Future[sup]TM[/sup].
The earth had become so overpopulated that everyone was assigned some small portion, maybe a few square feet each.
That’s all I got.
Maybe you mean Billennium by J. G. Ballard, but your description is too vague for me to be sure.
Did this story have the protagonist discovering a room that had been boarded up and forgotten?
Did Captain Kirk find himself alone on the Enterprise with some foxy blond chick?
No?
Then I got nuthin’, too.
Does the protagonist live in a cubicle on a staircase until he finds a new apartment? That’s also from “Billenium”.
I’ll try to track down a copy of Billennium and see if that’s it.