Water

Plumber and engineer came by early this morning, and between them determined that the water wasn't getting into the apartment from the roof, but rather, from a badly-designed little nook between my balcony and the next-door building. Instead of the water draining into a rain gutter right next to the nook, it infiltrated the walls and saturated my flooring.

Which means that not only does the flooring have to be replaced for about a third of my living room, but they've got to rip open a couple of walls to do ... I don't know. Re-plastering?

Headache still incoming.