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Crawl Space Mold

Musty odors and sagging floors are just the beginning of crawl space mold problems. Don’t let them get out of hand. Contact a professional.

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A crawl space is something normally kept out of sight and out of mind. Homeowners go about daily business hoping that, without some obvious signs, all is well within the four walls of the home. As such, the signs of mold in the crawl space often catch homeowners off guard. 

Mold, a problem resulting from a fast-spreading fungus, can take over an entire home in a matter of weeks. The moment any signs crop up, such as sagging floors, musty odors, high humidity, it’s time to take action so you can prevent any further damage to the home. Let’s explore what you can look for and how to stop the issue before it escalates further. 


Causes of Mold in the Crawl Space 

Mold growth inside of a home is not altogether an uncommon sight. Most crawl spaces, basements, kitchens, and bathrooms deal with mold at least once, but the danger is when they spread to other parts of houses unchecked. 

Most homeowners don’t spend many hours inside of their crawl spaces, which means the problem can start without anyone being the wiser. The best way to combat this mold problem is to understand how it starts, so you can prevent it. 

  • Cracks  

Foundation cracks are one of the main reasons behind mold growth inside of a crawl space. Cracks can form for many different reasons, such as shifting soil around the home or bad repairs. Likely to start at the base of a home, cracks will allow the elements to seep into your house and spread throughout otherwise well-conditioned areas. 

Cracks present a problem even if the weather outside is decent since it will allow any moisture from the surrounding soil to enter the home. With the moisture rising, mold will take hold and spread. Even an encapsulated crawl space may face this issue. That’s why it’s helpful to schedule regular inspections and to keep an eye out for any spreading cracks. 

  • Leaks  

A crawl space is designed to hold the inner workings of the home, such as the pipes and electrical wiring. When everything is in good working order, a crawl space is a convenient solution for keeping the inner mechanisms of the house safe and hidden from view. However, since pipes lead straight through the crawl space, there is a potential for leaks to go undetected. 

An undetected leak will lead to standing water which, with the heat of the space and the home, evaporates and increases the moisture in the air. As the moisture clings to structures inside the crawl space, it will continue to spread to other parts of the house. This can give mold a highway to spread. 

  • Water Events 

A water event can leave your crawl space full of water and, over time, a higher level of humidity. Such events usually include floods or burst pipes. These don’t simply leak over time but instead fill a crawl space with some measure of standing water. This can allow mold to take over. Even once the area has been cleaned out, there may be nooks or crevices that remain damp, and mold can thrive here.   

If your area experiences flooding, then it’s important to invest in waterproofing measures and even a sump pump. This will help repell water but also dry out your crawl space quickly if water does manage to get past. That limits how much cleanup is required, but also deprives mold of the chance to discover a foothold. 

  • Condensation  

In previous years, building codes required that crawl spaces are built with a source of ventilation toward the outside of the home in order to prevent any type of mold problems. Unfortunately, this ventilation can make mold problems worse. That’s because of how it lets in water and how it messes up the temperature balance. 

The temperature of the crawl space tends to be cooler than the greater outdoors, which only gets worse in the summer or spring months. As warm air comes into contact with the cooler air inside the crawl space, the air cools and releases moisture. This ventilated space then becomes a constant source of warmer air, which releases continuous amounts of moisture, leading to dampness. That may cause a mold problem to grow worse.  

  • Weather 

Weather has a large impact on what happens inside the home, especially in the crawl space. In areas like Toledo or Cleveland where rain and snow are common, the soil surrounding the home is likely to remain wet for most of the year. 

In dirt-floor crawl spaces, this dampness can seep up through the ground and raise the levels of humidity in a home. It can even lead to standing water after heavy rainstorms or during the thaw after winter. Aside from a full encapsulation, which should be conducted by a professional, there are no other ways to prevent or fix such an issue. 

Leaking basement

Signs You Have Mold in the Crawl Space 

Signs of mold aren’t always as obvious as a homeowner would hope. You may think of mold only as something you can see with your own eyes as it’s making its way up the walls of a house. In truth, mold can have other signs that manifest before any tangible spores or growths come into view. Keep an eye on “harmless” red flags like these: 

  • Smell  

A musty smell emanating from the crawl space is likely an indicator of mold. The instant you enter the space or check the entrance, you will catch a damp odor that may be slightly sweet. This smell is given off by the mold itself, but also any wood, furnishings, or stored items it’s beginning to eat away at. 

Although crawl spaces see less foot traffic, checking it once every few weeks or months should allow you to catch this problem sign. If left alone, mold can quickly spread into your walls, support beams, and any items stored in the crawl space. If given enough time, it may reach up into the rest of your home and begin affecting your health. 

  • Sagging Floors  

The older the home, the more likely it is that you’ll overlook sagging floors. It’s natural for certain problems to develop as your home ages. You should always pay attention if you notice that your floors are uneven, sag in places, or are slightly bouncy underfoot. That last sign in particular indicates moisture in the floors.   

Moisture easily leads to mold. Mold can spread into other parts of the house quickly by following humidity, dampness, or condensation. The floors above the crawl space are the first to feel the impact of the mold as it continues to make its way throughout the house. This will become more obvious with hardwood flooring, as some kinds of mold specifically target wood. 

  • Cold Drafts  

Cold drafts often mean the outside elements have access to the inside of your home. The crawl space is the largest culprit for this type of problem. Should a home feel drafty, making it especially uncomfortable to walk around barefooted, it could point to a poorly insulated crawl space (or one that has no encapsulation whatsoever). 

Crawl spaces are vulnerable to the stack effect. The stack effect causes cold air to come in through the crawl space, along with any moisture, and up through the house as it warms along the way. In the end, these drafts point toward a crawl space open to the elements and the buildup of moisture. This can lead to mold growing and thriving. 

  • Streaks on the Wall  

You may look for mold as little clusters of growth, thereby overlooking the streaks it can form on your walls. Mold will often follow wood and moisture, so if there are streaks of condensation or dampness within a support beam, you will see the spores following this line in a streak. 

Mold is able to adhere to nearly any surface, so it’s no problem for it to spread vertically. This is often the warning sign you find when the mold is spreading to other areas of the home. It will sink in through the walls, streak up along support beams, and find its way up through the floors of your house. 

  • Warping  

Mold eats away and weakens the drywall, wooden floors, and beams it touches. If this goes on for long enough, it can warp the surfaces it lives on, which is especially dangerous in the crawl space. You may see your support beams and joists beginning to twist, bend, or otherwise warp. You may also see wallpaper starting to bubble and peel away from your walls. 

Over time, this can compromise their ability to hold your property’s weight. That can lead to uneven floors, bowing walls, and even heavy structural damage. In the worst-case scenario, it can even lead to your foundation collapsing. 

  • Allergy Symptoms  

Apart from the effect mold has on the house, there are health symptoms that members of your home may suffer. This is one of the most dangerous outcomes. It’s also one of the most telling signs of mold that’s been thriving in your house for some time. Mold spores can be inhaled over time or come into contact with the skin. Some species of mold are not harmful, while others can even require hospitalization. 

Though not everyone is allergic to it, some people may also exhibit allergy symptoms without the need for long-term exposure. If a family member has allergy symptoms, check out the crawl space in case it is contributing to symptoms. Common signs include runny or stuffy nose, sneezing, coughing, itchy eyes, and more.  

  • High Energy Bills 

You may first detect the presence of mold in your crawl space because of your energy bill. A crawl space that’s battling with moisture and mold will have an increased level of relative humidity. If your crawl space isn’t properly encapsulated (or has no waterproofing at all), this can lead to the rest of your home seeing an uptick in humidity. 

Moist air is far more difficult to heat and cool than dry air. That will result in your HVAC system working harder than it needs to. Of course, it will burn more energy, and that’s very costly. If your energy bill seems to climb, it’s important to locate the mold, remove it, and safeguard your crawl space against humidity. This not only protects you against future mold growth but can also bring that grand total down.   

Crawl Space Mold


Many homeowners view inspections as a pointless way to spend precious dollars. Some might understand the importance of routine inspections but decide to go about the DIY option. Whether you choose DIY or hiring a professional, inspections are crucial to keeping a healthy home. 

  • Timing  

A crawl space is purposefully located in an area that has less foot traffic than other areas of the house. This means that any problem arising from a crawl space is likely to go on undetected for long periods of time. Homeowners don’t like looking down there, and that is not surprising with the weird smells and dark lighting. Most of the time, crawl spaces are around one to three feet tall, so there’s no reason to go down there even for storage. 

Even still, checking your crawl space is a great way to find problem signs and identify issues before they get out of control. No matter how unappealing, you should inspect your crawl space once every six to 12 months. If you’ve recently had a storm or are noticing an uptick in your electricity bill, then peek down there for a look right away. If you’ve had issues with your crawl space in the past, or your home is already vulnerable to mold, do this once every two to three months. Certain signs won’t develop immediately, so checking more often will let you catch what hadn’t yet properly manifested before. 

  • Signs  

Checking for odd smells, visible damage, and standing water can help you better inform an expert if you need to call for repairs or consultations. You can also look for cracks that are wide enough to fit a credit card into. If you see any damage to your crawl space encapsulation, like a torn vapor barrier, you can get in touch with a professional right away. 

Of course, it’s best to match this to an expert inspection every year. Without the experience and tools a professional has, it’s easy to overlook smaller issues or even misdiagnose what you’re seeing. For example, finding standing water could make you blame a leaking pipe when it’s really an issue with your soil. You could also misdiagnose different kinds of wood rot as black mold, which can lead to you applying the wrong solutions, letting the problem get out of hand in the meantime. 

Mold can grow inside of a crawl space completely unchecked since it’s off the beaten path. Before long, the level of mold, which spreads quickly from one space to another, grows to dangerous levels and has an impact on everything inside the house. The placement of the crawl space might make it tempting to ignore the problem altogether, but that should not be done under any circumstances because of the effects mold has. 

  • Dangerous to Home 

The integrity and safety of a home depend on it remaining mold-free as much as possible. Although certain species are rather harmless, others feed on organic material such as wood, fabric, and even drywall. That can lead to it eating away at your walls, flooring, support beams, and other parts of your foundation. 

Support beams and floors will start to get soggy and uneven as the mold destroys the wood on its way upward. Walls will start to look uneven and even shift in places since the lower beams are not able to support the full weight. It could eventually damage the structural integrity of your home and lead to a collapse in certain areas. 

  • Dangerous for Health  

Apart from being dangerous to the home itself, mold is also dangerous to the residents and pets living inside. Mold carries different spores which can affect any living organism, making them sick in the long run. People have been known to suffer from headaches, breathing problems, skin infections, and even mental issues after living in a mold-infested home for several weeks (or sometimes days). Those who suffer from asthma or allergies are bound to find their conditions getting worse, as mold spores tend to get airborne. 

If the mold issues get out of control, members of the household may need to leave while repairs are made and the mold is removed. This can be very costly and uncomfortable for everyone involved. If the effects on their health become severe, this could require medical attention ranging from doctor visits and prescriptions to hospitalization. As such, it’s never a good idea to leave mold to grow unchecked in your crawl space. Even if it’s out of sight for now, it won’t be out of mind for very long.  

Of course, having a mold problem once doesn’t mean you’ll have to deal with this issue on a regular basis. Once mold treatments are applied and the spores are removed, you can safeguard your crawl space from ever having a reoccurrence. In fact, if you apply these measures early, you can head off the problem long before it begins. 

  • Encapsulation  

Encapsulation involves sealing a crawl space off from the outside elements. This will keep out any water, air, pests, and temperature changes. It also means installing gear that will regulate the temperature and humidity of the space. The most noticeable improvement will be seen in dirt-floor crawl spaces, which are normally subjected to the great outdoors and whatever it brings. By making it a sealed unit, you can even use it for storage space like you would a basement. 

Encapsulation can’t be done DIY. There are many preparations that need to be made. For example, the crawl space will go through a dehumidification process. Drainage systems will be installed, and the area will be inspected for any kind of structural damage. When a professional gives the all-clear that your crawl space isn’t struggling with any hidden issues that were overlooked, only then can the main part of encapsulation begin. 

  • Waterproofing  

Water is the greatest threat to your crawl space, not in the least because it results in mold. When an expert waterproofs your crawl space, they will be installing gear such as sump pumps, dehumidifiers, vapor barriers, vents covers, and other equipment that help make your crawl space a sealed, well-regulated area. 

Of course, this will be customized to your unique home and the problems you face. For example, downspout extensions and perimeter drains will be recommended for homes that struggle with expansive soils or that see a great deal of flooding. For those that have pest issues or plan to use the crawl space for storage, thicker vapor barriers can be a great asset when paired with well-fitted vent covers. By tailoring it to your crawl space, an expert can ensure you’re at a far lower risk of developing mold in that space. 

Ohio Basement Systems Has All the Solutions You Need 

Finding (or even suspecting) mold in your crawl space is scary, both for your home and your health. Backed by a team of experts, you can get the problem resolved quickly and efficiently—and make sure it doesn’t reoccur. Ohio Basement Systems offers all of the tools and expertise needed to prevent, remove, and safeguard against mold.  If any damage is present, we can even help reinforce your walls, fix sagging floors, and strengthen your foundation, so you can get back to enjoying a safe and comfortable home. Get in contact to take advantage of a free inspection and no-obligation quote.

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