Hello, yes it is a floating floor. Unfortunately, I don’t know what is underneath as far as subflooring. I have tried to reach the company that put in the floor so they can tell us. It’s been a week and hasn’t gotten any worse so maybe it’s the exapansion issue as opposed to moisture.. Since it’s on a slightly higher level that the main floor, I hope that is the problem as it sounds less severe. I didn’t mention, but a few days before this happened, we had an exterminator treat that room for termites that we noticed had built a tunnel the week prior. Could the treatment create enough moisture to cause this?