Why Do I Have Crawl Space Mold?

If you’ve never dealt with crawl space mold before, you might not know what causes it. This knowledge can help you avoid crawl space mold in the future. Here are a few of the most common causes of crawl space mold. 

Warm Spaces  

Mold loves warmth and grows readily anywhere the temperature is pleasant. In general, however, mold considers temperatures pleasant to itself that are also pleasant to humans. That means it doesn’t have to feel warm to you for it to be warm enough that mold can grow in your crawl space. It just has to feel pleasant overall. 

Another reason the temperature in a crawl space tends to be perfect for mold is because it’s typically very steady. Although you might turn the temperature in the rest of your home up or down, the temperature in the crawl space will usually stay around the same because it rests underground and in a separate area from your home. 

High Humidity  

It’s also necessary that you have a relatively high level of humidity for mold to grow. However, this “high level” of humidity doesn’t necessarily need to be in the realm of 80-90%. Mold can start to grow and thrive at relative humidity greater than 55%, which is only slightly higher than the approximately 50% most crawl spaces should try to stay underneath. 

Although most people think of “high humidity” when they think of mold, it might be better to just think of “humidity” as being an important part of crawl space mold growth. After all, as you can see from the fact that mold can thrive at a relative humidity as low as around 55%, the relative humidity doesn’t need to be as high as it might seem. 

Standing Water or Condensation  

Even if you don’t have an extremely high level of humidity in the general crawl space, you can still experience crawl space mold if you have standing water or condensation of any kind in your crawl space. That’s because this water is, of course, equivalent to 100% humidity, and therefore, mold can grow on and around the water or condensation

This is exactly why you can’t just install a crawl space dehumidifier and expect that it will fix your mold problem. If you have crawl space mold issues, you need to fix them at the root rather than trying to fix the various symptoms. Only then will you be able to fix your crawl space mold, with or without a dehumidifier in the crawl space.  

Organic Material 

The final thing mold needs to grow is some kind of organic material. That’s why mold tends to happen on wood, drywall, and similar organic materials, but it rarely occurs on stone unless there’s an organic material in and around the stone that it can grow on. It feeds on the organic material to grow and move across these surfaces.  

One special organic material that mold really loves is cellulose. Wood floor joists tend to be extremely vulnerable to mold because they’re usually 40-50% cellulose, and cellulose is one of mold’s favorite foods. That’s why it’s so important to be extremely careful with your home’s wood floor joists, because they’re very vulnerable to mold.

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