My House Smells Musty, But I Can’t Find Any Mold

A few weeks ago I went to do a mold inspection in someone’s house and as soon as she comes to the door, that’s exactly what she told me. “My house smells musty and moldy, but I’ve looked everywhere and can’t find any mold.” She wanted a mold inspection and air sample testing done. But she did not know what she was going to do if the tests came back positive for mold. “What will I have to do, tear all the walls out to find where the mold is?”

She makes a good point. In some situations, there is clearly a “moldy,” musty smell, but no visible evidence can be found of any microbial growth in the house. In this case I did a visual inspection of the house and like she said, there was not visible signs of mold. I took a few air samples in different areas of the house. I told her if they came back positive, we would find the source without tearing all her walls out.

The next day the lab emailed me the results. There was a high count of aspercillius/penicillium (compared to the outside count). But more disturbing, Stacybautris, was also found in the air samples. This is the “black mold” that seems to be the most feared species of mold to most people. Where could it be coming from? A more thorough inspection would be necessary. If the tests came back negative, no further inspection would be needed regarding mold. If you can’t see the mold, and if the air samples come back indicating normal mold counts, there are no mold issues in the house. There might be other explanations for the malodor.

But what does the further inspection involve? I first inspect the attic. It is not uncommon for mold to grow in the attic, even if there is no leak. But in this case, the attic had no mold.

Next, I suited up and checked out the crawl space. These areas are notorious for trapping moisture and creating very humid conditions, then suddenly it becomes a breeding ground for microbial growth.
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Sure enough, the ground under the house was moist and it was very humid. As I got on my back, using my headlight, I could see mold on the floor joists and the sub floor above me. It covered about 80% of the floor joists and sub floor. Some areas were lightly covered with a white & green mold and other areas were a thick, black mold. This was clearly the source of the musty smell in the house. I pulled my phone out and took several pictures, so I could show the homeowner.

(On a personal note, crawl spaces are no fun. As I was crawling back to the crawl space entry, I passed a couple of dead mice. Spider webs were everywhere and very thick. Many years ago, when I went into my first crawl space, I was very claustrophobic. I did not think I would ever get accustomed to going into these dark places. I imagined I would see snakes and spiders and every kind of creature imaginable under houses. But I really have no exciting stories to tell about wild animals in a crawl space, though I have went into hundreds over the years. I have found dead mice, rats, and snake skins, but not really anything more than that. Except the time I went into a crawl space that had a sewage leak, and though I was in a water proof suit, it still freaked me out that I was crawling in the sewage with maggots. Sometimes I don’t think I get paid enough. Though I never would have imagined it that first time, I have gotten use to going into crawl spaces. But, I digress…)

I went back up and explained to the homeowner how the mold problem in the crawl space could be remediated. But the hard part was over. We found the source of the mold growth and why the house smells musty.

If a mold test confirms there is excessive mold in the air of a house, a thorough investigation will reveal, eventually, where the mold is coming from. What if I did not find mold in the crawl space. What would have been my next move? I would probably begin partially removing baseboards in the house and looking behind them with a flashlight for mold. If none is found, I would tap the partially pulled out baseboard back into place (in some cases, re-caulking might need to be done). Why baseboards? I have found the first place mold growth makes itself visible is between the baseboards and the drywall. If you find mold behind a baseboard, there is moisture getting to this area somehow and it is causing the growth. This area of the wall may need to be cut out to check the backside of the drywall and usually it has even more visible mold growth. Now the source of the problem can begin to be found.

Another option, albeit a bit of an expensive option, is to test every room in the house for mold. The lab results will reveal which room has the highest level of mold, then the room next to it will likely have the next highest level and so on. The room with the highest count is very likely to be the source of the microbial growth and it filters from that room to the other rooms.

So, if you have a strong musty smell in your house, it is usually an indicator that you have mold in your house somewhere. It may take an expert to find out where, but it can be found and remediated. Inhaling musty, damp air over long periods of time can be dangerous to your health. When you factor in that you are also likely breathing in very high counts of mold, it is definitely something you would not want to ignore just because you can’t “see” any mold in your house. So call some professionals in the mold field and get it taken care of.

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