So last night, I took off the drywall, where the water was coming from the downstairs bathroom. The insulation is dry, and the water seems to be just seeping under the bottom plate. It's coming from beside the shower. We have a homestay student living in our basement, so I guess he's been getting the floor really wet. I know in some countries, the whole bathroom is waterproof, they have a floor drain in the middle of the bathroom. So I told him not to get the floor so wet. Hope fully he understands. I think I'll run a bead of silicone caulking along the bottom of the baseboard too, to keep the water out. I showed him how to stick the shower curtain to the wall, so water doesn't come out everywhere too. There was no water leaking in to the floor drain this morning, so that's a good sign. He's also the first smoker we've had living in the house. We suspect he's been sneaking smokes inside, even though we told him he had to smoke outside. It smells like a cheap hotel room down there. I know some of the smoke smell will stay on his clothes, it's just such a powerful smell. I opened both the doors down there, and put on the bathroom, and kitchen fans. Hopefully that will help. It seems really humid down there too, so we'll have to make sure he's using the bathroom fan. We had another student down there for 2 months, and it didn't seem humid at all, so I don't think he's leaving the fan on for 30min. (we have a timer) like we told him to. Oh well, the joys of tenants.