Multistory buildings are a different animal, and I have no experience there.
FIrst question: Is the suds from when YOU are running a washing machine in your apartment, or is it from a common laundry, or coming at times you are not running the washer?
Venting is not the first thing that comes to mind. What I might suspect is that the laundry drain is not installed correctly, or is undersized.
I think some other guys will offer some more specific advice. You will probably have to find a plumber who is familiar with your building.