EDIT – This appears to the extent of the damaged area after I got the vanity out and pulled up the vinyl floor. Standard sized marker for scale.
First of all, I acknowledge that this is entirely my fault. Since covid hit and I’ve been stuck at home I’ve noticed that my bathroom is always more humid than the rest of the house though usually not by a whole lot (maybe 5-6%). It feels like there is moisture in the air when you go in there though. I’ve been running a dehumidifier in there to fight it but it’s been a pain. I did fix a leaky sink in there (I thought) about 6 mos ago and thought that was the problem it wasn’t.
I finally decided to get in there, tear things apart and figure out where this moisture is coming from. I know the tub/shower doesn’t leak. I ran my hands around and under the toilet and found no moisture there. That led me to the sink. The bucket I had under there to capture the drips I had left after I thought I fixed it. It had maybe 1/8″ of water in it so clearly my fix didn’t work. But that’s 1/8″ that’s been collecting for six mos. I ran my hands around the bowl and over the P trap and all the connections to the floor and found nothing. Ran the sink and found nothing. It’s obviously leaking but I have no clue where.
Then I decided to pull the vanity and look behind there. Unfortunately when they replumbed my house they just drilled through the vanity and didn’t cut notches to make it easy to access so I had to do surgery. I ended up finding [this] (https://i.imgur.com/QEvlPRC.jpg) and this. There is obvious mold on the wall. The drywall is mushy. Underneath the laminate is the old vinyl floor and the floorboards under it are mush as well. The area where the wall meets the tub you can actually reach back behind the tub and I think you can even get down into the crawl space area with your hand. This seems much worse than I thought but maybe I’m over reacting. Plumbers did work here (by my records) back in 2019 maybe. Other than exposing all of this and drying it out as best I can and cleaning the mold with mold armour I’m not even sure where to start here whether this is something I can fix myself or whether I need to call a pro or insurance or which pro to call or what?