How to Remove Mold From The Crawl Space

How to remove mold in the crawl space.

Crawl spaces aren’t exactly places homeowners like to visit frequently. Regular inspections, however, are essential for a healthy home. Here we will answer some common questions that homeowners have about mold in crawl spaces, how to get rid of it, and reveal some effective preventative measures.

Topics Covered

  • How common is mold in the crawl space?
  • How much mold in the crawl space is acceptable?
  • What is the average cost of mold removal in the crawl space?
  • What are the signs of mold in the crawl space?
  • Types of mold found in crawl spaces
  • How to get rid of mold in the crawl space
  • How to prevent mold in the crawl space

How common is mold in the crawl space?

Mold in the crawl space is a lot more common than one would think. After all, it’s dark, damp, and has insects – no wonder no one likes to go down there to check. But when someone finally does go to check, they will usually find white, yellow, or black mold in the crawl space.

How much mold in the crawl space is acceptable?

The answer is zero. Even a little bit of mold in the crawl space can quickly spread and become a major infestation. Not only will this eventually lead to structural defects, which costs a lot of money to repair, but it also negatively affects our health.

What is the average cost of mold removal in the crawl space?

There is no average cost since it all depends on the severity of the infestation and whether or not the mold has caused structural damage. However, expect to pay around $500 for the removal of a small mold outbreak in the crawl space. With repair work included for damage to the structure can cost upwards of $30,000.

As you can see, mold in the crawl space is something that should be taken seriously, and the problem needs to be dealt with rather sooner than later.

What are the signs of mold in the crawl space?

There are a number of telltale signs. Some of these include a distinct musty odor inside of your house, while there are no visible signs of mold growth. Another clear sign is allergic reactions whenever you are inside the house.

In more severe cases, the ground floor of the house starts sagging. That is a sign of significant structural damage caused by the mold in the crawl space. It leads to doors getting jammed and the mold spreading to the ground flooring/carpets.

Types of mold found in crawl spaces

There are many thousands of mold species in existence, but only a handful of them are most commonly found in homes, or crawl spaces, for that matter.

Stachybotrys chartarum

Stachybotrys chartarum, or toxic black mold as it’s also known as is one of the most dangerous mold species you will find. Unfortunately, it’s no stranger to countless households around the world. It has a black or dark green appearance, but just because you found a black colored mold in your home, does not necessarily mean that it’s Stachybotrys chartarum.

The only way of accurately knowing if the black mold is indeed Stachybotrys chartarum is by doing a test.

If you know for sure that you have toxic black mold in your home, then it’s strongly advised that you not deal with it yourself and call in a professional mold removal company.


Alternia is one of the most common types of mold found in crawl spaces and can have a gray, green, or black color. Short term exposure to Alternaria leads to allergic reactions such as coughing and sneezing. In contrast, longer-term exposure to particular types can cause more severe health effects – especially in those with compromised immune systems.


Penicillium mold is commonly found on dead organic matter, in soil, rotting food, and yes, sometimes the crawl space underneath your house too. It’s usually a green, yellow, or blue-colored mold that causes allergies and breathing problems.


Aspergillus is probably the most common household mold, and the good news is that it’s mostly harmless to healthy individuals. People with weakened immune systems, on the other hand, are more than likely to experience problems with this mold as it causes allergic reactions such as sinus, headaches, and in more severe cases, lung infections. Aspergillus mold can appear black, yellow, or green.


Cladosporium is a common green or black species of mold found in the crawl space. It has some pretty adverse effects on people, especially among those with asthma and compromised immune systems.

How to get rid of mold in the crawl space

Getting rid of mold in the crawl space can range from easy to extremely difficult and labor-intensive – all depending on the severity. It would be better to call a mold remediation company to deal with large outbreaks that you do not feel comfortable dealing with. On the other hand, if it’s not too major, we will show you how to safely and effectively get rid of the mold yourself.

Killing mold within the crawl space will be done in two stages. In the first, we will kill all existing mold and spores. The second stage is much harder as it will require you to go down there and wash mold growth off from surfaces – but we will also be showing you a quick and easy way to do that.

Stage 1: Killing mold growth and spores

In the first step, we will fumigate the crawl space to kill all existing mold and spores.

Don’t worry; it’s a lot easier than it sounds.

For this, we will either need a couple of mold bomb foggers or a mold fogging machine. We have reviewed and provided all the necessary information about both on our mold bomb foggers page.

I would personally recommend throwing a couple of BioCide mold bomb fogger cans into the crawl space. Not only will it kill all the mold and spores down there but also all kinds of bacteria and viruses.

Stage 2: Removing the mold

Now that all the mold is dead, you will have to go down there to remove it from the crawl space structures physically.

Physically removing it is not too hard if it’s only a few spots here and there, but if it was more widespread, then the task becomes significantly harder.

If there weren’t a lot of mold in the crawl space, then you can simply scrape it or wash it off with warm soapy water. Removing larger mold outbreaks in the crawl space is a lot more labor-intensive, and for such a task, it would be best to rent or buy a surface blaster kit.

Safety precautions:

Dead mold spores can still cause allergies and be toxic. Therefore, it’s best not to take any chances and wear a respirator mask, gloves, and old clothes that you can discard as soon as you are done.

How to prevent mold in the crawl space

In some cases, mold in the crawl space can be an expensive nightmare to remove. Why risk the inevitable when you can take steps to minimize the chances significantly of mold forming in the crawl space in the first place?

Here we will show you how to do just that.

Inspect the outside of your home: There are two things to look for when inspecting the outside of your home. The first thing to look for is whether or not the gutter downspouts are directing water away from the foundations of your home. This is particularly important because if it doesn’t, then rainwater will accumulate around your house and seep into the crawl space.

The second thing to look for is cracks and openings along the bottom walls. These should be fixed and sealed off so that nothing, especially water, can enter the crawl space.

Control humidity: Mold starts growing when humidity levels exceed 60%. Therefore, the chances of mold formation are drastically reduced when keeping humidity levels in the crawl space below 60%. Doing so is easy with the right type of dehumidifier.

More Information

Mold bomb foggers.. do they really work?

The best crawl space dehumidifiers reviewed

Sump pumps, when do you need one?

How to remove mold from the basement