What Qualifies as a bathroom

[Frank Mumford]

I have a tub, toilet, sink, and vented fan in a basement area that is closed off from the rest of basement. It is open to the storage area, utilities, washer and dryer.  This space takes up half the basement and has doors to it, but with our last appraisal, they listed the house as only having 1 bathroom; not two.  We live in Minnesota.  I am trying to figure out what I need to do; do I need to close off the bathroom to the furnace and storage room, but is it ok to keep it open to the washer and dryer?  Thank you!