Everything You Need to Know About Crawl Space Mold

Everything You Need to Know About Crawl Space Mold

In this comprehensive post, we'll go over;

The most common questions associated Crawl Space Mold.

You'll learn;

  • What a crawl space is.
  • Causes and Signs of Mold.
  • The types of moisture and mold within a crawl space.
  • The estimated cost of crawl space mold removal.
  • How to prevent the mold in the first place.

So if you've ever asked yourself any of these questions, you'll love this post!


Crawl Space Mold in Rochester, NY

Some homes have a basement, and some might be on stilts. Some may be on a concrete slab, and other homes might have a crawl space. But do we really even know why?

Is one type of foundation better than another? Well, it really depends on where you live, the property grade (does it slope?), and the soil type. 

With that said, some foundations might be more prone to mold than others, like basements and crawl spaces. Keep reading to learn everything you need to learn about mold in your crawl space!

What Is a Crawl Space?


For most, a crawl space is usually a small dark space between the ground and the first floor of a home. This space acts as the foundation of the home.

Most crawl spaces are only a few feet tall, leaving room to only crawl around (hence the name). Some crawl spaces can be similar in size to a basement though, but not as often.

When built correctly, the crawl space can allow for easy access to the plumbing, wiring, and HVAC systems of a home. Additionally, it can be more cost-effective to have a crawl space instead of a full basement. 

If the crawl space is poorly designed, poorly built, or ventilated incorrectly, the area can end up having moisture build-up, insect/rodent infestation, and even worse, mold.

Most people just ignore the crawl space until they need to get in for whatever reason, by that time it can be too late and a problem has likely already occurred.

Causes and Signs of Mold in Your Crawl Space

Mold needs moisture and organic materials to grow and thrive. Crawl spaces are known to be dark and damp, creating a perfect place for mold growth.

In Rochester, NY, and surrounding areas, we know about humidity all too well. Be on the lookout for these numerous causes and signs of mold in your crawl space:



Open Vents - Until recently, it was believed that crawl spaces should be vented to help “breathe”, however, the air from outside can be humid and filled with moisture.

Standing Water - Can be caused by an excessive leak or plumbing damage

Overly wet soil - Can be caused by heavy rainfall, snowmelt, a recent flood, or burst pipes

Moisture - Humidity and condensation within a crawl space can cause major damage to the area. Any wood materials used in the crawl space can soak up the moisture from the air. If the moisture within the wood starts to reach 20%, there is a risk for mold and rot to begin growing.



Constant Respiratory Illness - Itchy, watery eyes, runny nose, coughing/sneezing, pneumonia, asthma, and other chronic illness can be caused by mold allergies or the presence of toxic mold.

Visible Mold and Condensation - seeing patches of mold around the baseboards inside, or seeing mold/condensation within the crawl space will ensure a moisture and mold problem.

Odor - Mold and mildew have a musty, damp smell. If you start smelling it in your home, that is a sign of mold.

Cold air coming into your home - When crawl spaces are vented, outdoor air will enter. That air will settle within the crawl space until it warms up, and eventually, it will rise up into the home. This is called the “stack effect”.

We know that hot air rises, and the air from the crawl space will eventually rise into the home. Spaces without ventilation will not get any outdoor air, therefore the air won’t travel into the home.

Crawl Space Insulation - missing or sagging insulation can be a sign of water damage

Pests - If you notice insects, rodents, or small animals getting into the crawl space, it is very likely that there could be a problem causing damage.

Buckling or Warping Floors - When the flooring starts to appear damaged, there could be a problem underneath, within the structure of the crawl space. Wood rot and mold caused by water damage play a major factor in structural damage.

Types of Mold and Moisture in Crawl Spaces


We have previously learned that there are over 100,000 species of mold. So how do we know what kind of mold can be found in crawl spaces? In most cases, there will be various types of mold.

Most will appear on surfaces of the crawl space. This can include floor joists, walls, and even the dirt floor. Surface mold can be cleaned off and usually doesn’t cause any structural damage. 

When there is damage, it is likely coming from a fungus that decays. This type of fungus can make wood look spongy or wet. It might even feel soft.

Many people have heard of “dry rot”, and this is a type of decay fungi. When there is a large amount of this type of damage, the structure can be at risk and may no longer be stable. 

Additionally, there is often a white mold in crawl spaces. It can mostly be found on soil and floor joist surfaces. Like other types of mold, it can still be harmful and possibly produce toxic spores.

When it comes to the moisture that gets into a crawl space, it can either be caused by condensation, rising dampness, or penetrating dampness. Rising moisture will come from the ground.

In crawl spaces that are not sealed, ground moisture will travel up and can eventually seep into the floors of your home. Penetrating dampness is caused by leaks in plumbing or HVAC systems, flooding, or any other source above or within the crawl space. 

Condensation occurs when the crawl space is vented. Outside air comes into the crawl space and might be warmer than the air within.

When humid or warm air cools, the moisture gets released and can settle. Unsealed crawl spaces will almost always have moisture due to condensation.

Mold in Crawl Space Removal Cost

Mold Remediation costs for a crawl space can range anywhere from $500 to $5,000 and higher. Depending on the amount of damage the mold has caused will depend on how much work needs to be done.

Additionally, if the crawl space is extra small, or hard to access, the costs could increase. Since mold needs moisture in order to grow, it is very likely that there will be other necessary repairs. 

Cleaning and removing the mold may not solve the problem if the mold was caused by an underlying issue such as a leak or from not having a moisture barrier.

It is advised to have professionals come in, not only because the space is small, but they are trained in the potential hazards that may arise from the mold problem. 

There are DIY options, such as using a Crawl Space Mold Fogger that can be found at your local Home Depot. They are a cheaper alternative (about $50) and can eliminate existing mold and help prevent it from coming back.

However, if the problem that caused the mold is not resolved, it will continue coming back and potentially damage your home or start affecting the health of you and your family.

Preventing Mold in Crawl Spaces

vapor barrier

Don’t let the cost of crawl space mold removal scare you. There are ways to prevent the mold from growing in the first place.

  • Having a Crawl Space Vapor Barrier installed to prevent airflow, as well as ground moisture from seeping in.
  • In a sealed crawl space, using a dehumidifier will keep the space at an acceptable level (less than 50%)
  • Keeping gutters and downspouts clean and ensuring water is being moved away from the home
  • Close off or seal any existing vents to prevent outdoor air to flow into the crawl space. This also reduces the risk of frozen or burst pipes.
  • If you don’t have a vapor barrier installed, it would be recommended to do so. Additionally, a sump pump may be useful if there is enough space.
  • Inspect walls and flooring for cracks. If there are any, no matter how minor it is, call a professional for repairs. Leaving the cracks alone will allow for water and moisture to seep through.
  • Be sure that any plumbing and HVAC systems are functioning properly and undamaged. 
  • Any exhaust vents within the home (dryer vents, bathroom vents) are going outside and not into the crawl space.
  • Keep the crawl space free from debris, clutter, or anything else. Crawl spaces are not to be used as “extra storage” unless it is fully encapsulated.
  • Most importantly, keep the area dry and moisture-free.

Crawl spaces can be a great cost-effective way to hide the “guts” of your home systems. When done right, there is no need to worry about the air quality within your home.

Did you know that at least 50% of the air you breathe on the first floor of your home comes from your basement or crawl space? Even though a crawl space can be prone to mold, there are plenty of ways to prevent it.

Any problems should be taken care of right away to help prevent further damage. 

Rock Environmental is certified in mold remediation and follows all safety regulations. Additionally, we are IICRC certified and HAZWOPER trained.

We will also work with your insurance company. That is proof that we’re in this together! 

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