I have 2 guests shared 1 bathroom upstairs, both lived over 1 month with bargained price (23%-25% off , both are interns). During their stay, one day I found a deep scratch on the shared bath's floor. I couldn't figure out who did it. Today, when I did cleaning I found cracks around that scratch. There used to be a sink underneath so this floor got some hollow area underneath without support (6“ diameter I believe? poor job done by former house owner). I know one of the two folks is abusively using my house , he do laundry from 5pm till 1am usually on weekends, slammed doors during midnight without any concern everyday. Two men used 380sheets toilet paper in 3 days usually, so averagely they use 63 sheets toilet paper to clean every day, or 24ft (7.25m) / day / person.
Now it's shared bath, the floor has less support, I couldn't find who did it. I have been living, hosting guests for 1 year without issue. How can I address this floor damage? How to claim damages?