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Mold on wooden beams in the crawl space of a home

Crawl Space Mold

A moldy crawl space is not only unsightly, but very unhealthy and unsafe for your home and your family.

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Finding mold in your crawl space can be very worrying for many reasons. It’s important to know that a moldy crawl space could have negative impacts on your health, and that could be a serious problem. Here’s everything you need to know about your crawl space mold and crawl space fungus problems.

Do These Crawl Space Mold Pictures Look Familiar?

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.

It’s important that you pursue a permanent fix for crawl space mold, not just a fix that will last for a few weeks or months. This process will usually be the process a crawl space expert will help you go through for permanent mold removal.  

Remove the Existing Mold 

The first step should be to remove existing mold from your crawl space. Whether you’re dealing with very small spores of mold or you’re dealing with gigantic sheets of mold, you need to remove the mold before you can get to work making your crawl space inhospitable to mold. Otherwise, the work will go on around those mold spores. 

Of course, mold removal is a pretty dangerous process. Although most mold isn’t always toxic, it can still do a number on your lungs. That’s why most mold removal requires breathing and eye protection. It’s important that you consult a mold removal expert for this rather than trying to do it yourself, because that can be extremely dangerous. 

Encapsulate Your Crawl Space  

With crawl space encapsulation, you’re addressing the root problem rather than just tackling the symptoms. That’s right: mold growth is a symptom, not an initial problem. When you’re experiencing mold in your crawl space, it’s because of that crawl space humidity, and if you remove your crawl space humidity, you’ll be able to stem mold growth. 

Crawl space encapsulation is a process that can be difficult to complete, but it’s absolutely worth it. On top of avoiding future mold growth, encapsulation can lower your energy bills, help you avoid high indoor humidity, and make it less likely that you’ll encounter wood rot. These are just a few of the reasons people opt for crawl space encapsulation.  

Install a Dehumidifier 

Typically, crawl space encapsulation utilizes a dehumidifier, but it’s an important enough step that it bears repeating. It’s important that you install a dehumidifier in most cases to help keep your crawl space humidity down to a manageable amount, even if you only have to install this dehumidifier in your home for a short period of time. 

Whether you install it for good or you have it in your crawl space temporarily, a crawl space dehumidifier can be very useful for avoiding future mold growth. After all, as long as you’re paying attention to make sure you don’t end up with standing water or condensation, an energy-efficient dehumidifier can essentially ensure that your crawl space stays mold-free. 

Observe General Crawl Space Maintenance  

Once you’ve removed the mold from your crawl space, you need to make sure you’re observing crawl space maintenance as a whole. This will help make sure the mold is truly gone for good, which is an important part of this process. There are a number of things you should do as a part of your crawl space maintenance every so often. 

For example, it’s a good idea to do a crawl space inspection at least once a year. With a yearly inspection, you’ll be able to see whether mold is happening in your crawl space and catch it before it has a chance to spread. Additionally, you should keep track of any potential symptoms of crawl space mold and let your inspector know about them when you get in contact for your yearly maintenance.

Although most people have a natural fear of crawl space mold, some people wonder whether it’s really important to clean it out when you find it. These impacts are just a few of the more significant ones you’ll find if you don’t fix the crawl space. 

Physical Impacts of Mold on Organic Materials  

You already know that mold requires organic materials to grow, but what you might not have realized is that this growth isn’t wholly innocent. In fact, mold essentially “eats” these organic materials, breaking them down into a slimy mass you may have unfortunately seen in your own crawl space or other areas of your home. 

In this concept, it’s extremely important for you to clean up mold as soon as possible. If you don’t clean up the mold, you run the risk of the mold continuing to eat through whatever organic material it’s on. After a period of time, which may be very long or very short, those organic materials may fail, leading to foundation failure in your home. 

Musty-Smelling Crawl Space and Home 

When you say you have a “musty-smelling” area of your house, you’re really smelling the mold that’s growing in the crawl space. As air moves up from your crawl space into the rest of your home, that mold may settle into other areas of your home, and you may end up with that smell all over your home. 

Without considering the health effects of the mold spores floating through the air, this musty smell can be very distasteful. It’s common for people to hate the smell of mold, and having that smell become all but permanent in your home can be extremely frustrating. Whether it’s borne of a health concern or just an aesthetic one, removing the musty smell is a driving factor for some people in their choice to tackle mold problems. 

Respiratory Issues and Allergies  

One thing mold is very good at is igniting respiratory concerns and allergies. If you already have an allergy to dust, for example, you will probably have wildly exacerbated allergic reactions if there are mold spores in the air. If you have respiratory concerns like asthma, mold spores can make your asthma much worse on a daily basis. 

If anyone in your home has allergies or respiratory issues, it’s crucial that you solve your mold problems to make sure these issues don’t become a strain on their quality of life. If you find that all of a sudden your family members have started to experience these issues, you may also want to question whether mold may have taken root in your crawl space.  

The Stack Effect 

Possibly the biggest reason for all of these problems is something called the stack effect. When you have an opening for air in the lower area of your home, like open crawl space vents, and an opening in the higher area, like attic openings, you’re creating an expression of the stack effect. This causes air to enter the crawl space, warm up, then move up throughout the home. 

The thing is, as the air moves up through the home, it’s not really just air that’s moving. You’ll also see tiny particles of any airborne materials that move up. This may include mold spores, dust mites, and moisture, among other things. That’s why it’s so important to encapsulate your crawl space entirely; if you have no entry for air from the bottom, you won’t have to deal with the stack effect .

Create a Crawl Space Free of Mold with an Expert’s Help

The only way you can really determine whether your crawl space is free of mold and fungus is to consult with a crawl space repair expert. Even if you think you know about your crawl space’s moisture problems and you feel like it’s not a big deal, there’s no way to know whether you have mold unless you request an inspection and have someone physically check.

Whether or not you find fungus or mold in your crawl space, it’s important to have this type of inspection regularly so you can catch it as early as possible. A crawl space repair expert will be able to do much more with small amounts of mold than if you have huge swaths of fungus or mold covering your crawl space. Request an inspection from JES as early as possible if you believe you might have mold problems.


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