Black mold? Not sure. Need help.
I recently bought an older home. I've been in it now for about 6 months. About 2 weeks ago, my wife and I (who have allergy problems) began experienceing sinus headaches and things of that nature. I've always had bad allergies, but never sinus headaches really. Anyway, The house had some visible mold problems when i moved in, primarily the bathrooms that were unvented. I vented the bathrooms and cleaned up the mold and there is none reappearing. The house does not have that mold smell I have smelled before. It smells like an old house if that makes any sense.
Under the house, the previous owner said there was a moisture problem 10-15 years ago to the point that he had to replace the sash at the back of the house and fill in the foundation in a couple spots. Upon investigation, everything is dry as a bone, or at least not visibly damp anywhere. But on some of the floor boards inbetween the support beams, there is a hard black substance on a lot of the floor boards. It almost looks like small splatters of tar. But there isn't really anything like that on any of the old support boards and joists immediately beneath these floor boards. The black stuff is hard to the touch and does not really come off. I have sprayed it with bleach and scrubbed it with a wire brush but it doesn't really come off or show any signs of being affected by the bleach. Any ideas what this could be? It doesn't seem to be mold, but I don't know. I've seen what mold usually looks like.
I had a mold test done before we moved in and the levels were supposedly not elevated. The levels in the house were about half of that from the sample outside. So I was told this was not considered elevated or a problem by my real estate agent and the inspector. Plus, since then I have cleaned up effectively any mold I have found. There is no visible moisture problem anywhere that I can find.
Any suggestions? Health wise my wife and I have experienced some bad sinus sinus problems on occasion in this new house. But nothing too horrible. Plus it's Spring and we live in SC now - and the part of SC we live in is supposedly bad for allergies. We moved from the mountains.
Just curious if anyone could know what this black substance might be. Very hard, black, and it looks like little specks of tar. Does not respond to bleace and literally have to get a nail to scrape it off.
Thanks for any help or theories in advance!