Chances are, there’s concrete somewhere in your home. The material is durable, long-lasting, and can withstand harsh weather conditions. It makes sense that over two-thirds of new homes are built on concrete slabs. That being said, this material isn’t impenetrable. Mold on concrete is a problem that affects not only the structural integrity of your home but also the state of your indoor air quality. 

Understanding the causes, signs, and remediation methods for mold on concrete is essential for maintaining a healthy living environment and the longevity of your property. With so many homes having concrete somewhere on the property, this is a tidbit of information we should all know! With that in mind, here’s everything you need to know to ensure your home doesn’t get bogged down by hazardous contamination.

Can Mold Grow on Concrete?

When you think of concrete, you might initially think of an impermeable, permanent stone material. While concrete is certainly rock-like and can last for decades if properly maintained, it’s far from impermeable. Concrete is actually quite porous, and porous materials can potentially harbor mold. 

What does high porosity mean? If you were to observe a concrete block under a microscope, you’d see something similar to the moon's surface, with pits and bumps covering the surface. While concrete does not act as a food source for mold, these nooks and crannies can collect materials like pollen, dirt, skin cells, or any other number of organic compounds that can act as a food source. These pockets can also trap and harbor moisture, creating the perfect conditions for microbial growth to settle in if a lucky spore lands on the surface. 

Once mold has taken hold in concrete, it can begin to grow roots, further deteriorating the concrete, increasing the number and size of the pits, and allowing more materials to be captured for the mold to eat. This will go on until actions are taken to stop the growth.

Is Mold on Concrete Dangerous?

Indoor microbial growth, including mold on concrete, is not beneficial to our health. Once a colony is established, it releases spores, fragments, and sometimes toxins into the air around it. To make things worse, bacteria thrive in similar moist environments and release tiny particles, further lowering air quality. These small particles can easily be inhaled, absorbed through the skin, or even ingested. Some are so tiny that they can bypass the lungs and go straight into the bloodstream, which is where they can cause real trouble.

Since mold is practically everywhere, it’s normal to encounter a few spores and particles throughout your day, and in most cases, that’s not a big deal. Your immune system kicks in, handles it, and clears them out.

But living with an active mold problem inside your home—like mold on concrete—it’s a whole different story. You’re not just breathing in a few particles here and there; you’re constantly exposed to a concentrated "cloud" of them. This overwhelming exposure can overwork your immune system, potentially causing it to malfunction. That’s when you start seeing symptoms of mold exposure. Mold toxicity can also impact other health issues, such as Lyme disease, Mast Cell Activation Syndrome, Chronic Inflammatory Response Syndrome (CIRS), Chronic Fatigue Syndrome, and more.

Common symptoms of mold exposure include:

• Runny nose
• Rashes
• Hair loss
• Neurological problems
• Mood swings
• Watery eyes
• Persistent cough
• Digestive issues
• Chronic fatigue
• Brain fog
• Respiratory problems

The tricky part is that everyone reacts differently to mold. Genetics, underlying health conditions, the species of mold, whether it’s producing mycotoxins, the strength of your immune system, and how much you’re exposed to all play a role in how it affects you. People with weakened or developing immune systems, like young children or the elderly, are more likely to feel the effects of mold exposure faster and more intensely.

It’s important to remember that all types of mold, even if they don’t produce dangerous mycotoxins, can still negatively impact your health. Avoiding mold exposure, including mold on concrete, is crucial for maintaining good indoor air quality and overall well-being.

What Does Mold on Concrete Look Like?

The first step in dealing with mold on concrete is determining whether there is a problem in the first place.

Here’s what to look out for:

Discoloration: Mold often appears as patches or streaks of different colors. It can range from:

• Black or dark green (common with molds like Stachybotrys or Cladosporium).
• White, grey, pink, or light-colored (common with molds like Aspergillus, Mucor, and Cladosporium)
• Yellow, orange, or brown (common with molds like Aspergillus and Epicoccum nigrum)

Texture: Different species of mold grow in certain textures or structures. These can include:

• Fuzzy or Velvety: Some mold colonies have a soft, fuzzy texture and can look fluffy or cotton-like.
• Slimy or Wet: Especially in areas with high moisture, mold can appear wet or slimy to the touch.
• Powdery: White or light-colored mold may appear as a fine powder on the surface.

Mold on concrete also often grows in irregular patterns or spots. If left unchecked, it can spread into larger areas, particularly in corners, cracks, or crevices where moisture accumulates.

Where Should You Look?

Knowing where concrete is in your home can help you better keep an eye on this material to ensure it’s not being impacted by microbial growth.

Mold on concrete can commonly be found in these areas:

• Basement Floors and Walls: Basements often have high humidity and are prone to moisture issues from groundwater, leaks, or condensation, creating ideal conditions for mold growth on concrete.
• Garage Floors: Poor ventilation and moisture from vehicles, wet equipment, or humidity can allow mold to develop on garage concrete floors.
• Patios and Walkways: Concrete surfaces exposed to outdoor elements like rain or snow, combined with lack of sunlight and poor drainage, can foster mold growth.
• Shower or Bathroom Floors: Concrete in bathrooms, especially if not properly sealed, can trap moisture and provide a breeding ground for mold.
• Crawl Spaces: Concrete in crawl spaces, which tend to be damp and poorly ventilated, can also support mold growth.
• Foundation Slabs: If the foundation slab has cracks or is exposed to moisture seepage, mold can grow in these areas, especially if the slab is in constant contact with wet soil.

Special Note:

Homes built in tropical climates often use concrete as a primary building material, and they do so for several reasons: concrete is generally more resistant to moisture and humidity than timber, especially softwood varieties. It can provide natural cooling to a home and additional protection against tropical storms. As mentioned, though, it’s far from impervious to mold growth, and in these areas that have a higher relative humidity year-round, growth can occur without proper maintenance.

Other Signs

Don’t just rely on visibility, though. Sometimes, mold can be hidden. In that case, pay attention to these other indicators as well.

2. Odor

If you don’t find any visible issues, that doesn’t mean there isn’t a problem. It’s also important to rely on your nose.

Mold growth often creates a damp, musty, earthy smell due to the release of gases called microbial volatile organic compounds (MVOC). If you smell this, you may be dealing with a contamination situation.

3. Chronic Health Issues

Our bodies are incredible warning systems that will alert us if something’s wrong, including a contaminant in our indoor environments. It’s up to us to listen to these signals and figure out the root cause so that it can be eliminated.

If chronic symptoms suddenly appear and worsen near specific parts of the home, this can be your body’s way of saying, “Hey, something is not right here.”

How to Get Rid of Mold on Concrete 

If you notice mold on concrete in your home, don’t just reach for bleach—it won’t solve the problem or improve your indoor air quality. The best approach is to hire professionals who can properly address the issue. 

To truly handle the situation, all contamination has to be removed. This includes the mold roots, spores, fragments, mycotoxins, and bacteria. For porous materials like concrete, it usually requires a high concentration of hydrogen peroxide or similar treatments to fully decontaminate, and that’s a job best left to professionals.

It’s also tough to figure out how far the contamination has spread. Is it just on the surface, or has it penetrated deep into the concrete or even spread to other parts of the house? Professionals have the expertise and equipment to assess the full extent of the problem and handle it accordingly.

Hiring professionals ensures your home becomes safe, and the mold is fully dealt with. Unlike drywall, replacing damaged concrete isn’t always simple or cheap, so proper remediation is key to avoiding further damage.

Finding a Mold Inspector

The first step is to hire a qualified mold inspector. This person is crucial to the entire process, as the data they collect helps create a detailed plan for how the remediation team will tackle the contamination. Not all mold inspectors are equally qualified, so it’s important to choose someone with a solid reputation.

Your inspector should spend hours thoroughly inspecting your home's interior and exterior, using multiple measuring methods to collect as much data as possible.

Hiring a Remediation Team

Once the inspector has gathered the necessary information, your next step is to hire a remediation team, like HomeCleanse, to remove the mold. However, just like mold inspectors, not all remediation teams are created equal.

You want a team that understands how important it is to prioritize your health, knows how to create a safe living environment, and has a track record of successfully remediating homes with mold issues. 

A good team will follow a protocol based on three essential steps:

1. Properly remediate all mold sources.
2. Identify and address the underlying issues that caused the mold growth.
3. Remove all contamination, including spores, mycotoxins, and bacteria.

Skipping any of these steps leads to incomplete remediation.

If the root cause of the mold isn’t addressed, the same conditions that caused it will still exist, allowing the mold to grow back. If any part of the mold colony is left behind—such as the roots or spores—the problem can return. If harmful byproducts like mycotoxins or bacteria are not fully removed, you’ll continue to be exposed to dangerous contaminants, which can worsen or prolong symptoms.

The last thing anyone wants is to spend time and money on remediation only to feel sick because the job wasn’t done right. A trustworthy remediation team will check all these boxes so you can be confident that once they’re done, that mold on concrete is truly gone.

How to Prevent Mold on Concrete 

The best way to deal with mold on concrete is to avoid it in the first place! 

When it comes to preventing growth on concrete, air flow reigns supreme. Many, if not most, instances of growth on concrete result from improper construction methods and planning, leading to insufficient airflow in a basement, crawl space, etc. Air flow helps regulate humidity levels and, in doing so, helps keep concrete dry. A great idea is to bring in an expert to assess the home and identify any potential problems that could lead to improper airflow and moisture buildup. Make a list and address each area of concern when the budget allows so that you can avoid mold on concrete.

From there, focus on moisture. Without water, mold cannot grow. Fans and dehumidifiers can help supplement poor airflow and keep microbial growth at bay by eliminating humidity. Your goal will be to keep levels between 35-50%. Leaks should be addressed, and drainage and landscaping should be graded so water flows away from the home’s foundation. In a finished basement, building materials should be installed on standoffs so that drywall, for instance, is not directly in contact with a concrete foundation. 

Lastly, mold and moisture-resistant paints, primers, and coatings can be applied to concrete to enhance its resistance to mold growth and moisture in general.

One final point to consider is efflorescence. Efflorescence is a crystalline salt deposit left on concrete surfaces when moisture evaporates into the surrounding air. It can appear as white, textured patches raised off of the concrete’s surface. One might see efflorescence and fear that they’ve discovered a huge colony of mold, so be mindful of this before panicking. 

You can use The Dust Test to determine whether it’s a microbial growth problem. While efflorescence is not mold and should not be treated the same way, it still represents an issue involving moisture on concrete. In short, it’s a sign that further investigation is needed to determine the source of that moisture. 

Other Tips Include:

• Seal Concrete: Apply a mold-resistant concrete sealer on areas like basements, garages, or patios to create a barrier that reduces moisture absorption.
• Improve Drainage: Ensure gutters and downspouts are clean and working properly.
• Install Vapor Barriers: For concrete floors in basements or crawl spaces, installing a vapor barrier beneath flooring materials to block moisture from the ground.
• Use Exhaust Fans: In moisture-prone areas like bathrooms and laundry rooms, use exhaust fans to remove excess moisture from the air.
• Ensure Crawl Space Ventilation: Keep crawl spaces well-ventilated, and consider installing vents or fans if needed to allow airflow.
• Remove Organic Matter: Clean concrete surfaces regularly to remove dust, dirt, or organic materials (leaves, wood, etc.) that mold feeds on.
• Use The Right Cleaners: Clean concrete surfaces with botanical cleaning products to properly and safely remove particles from the surface. 
• Pressure Wash Exterior Concrete: Use a pressure washer periodically to clean exterior concrete patios, walkways, or driveways.
• Insulate Cold Concrete Surfaces: In colder climates, condensation can form on cold concrete surfaces. Insulate these surfaces to reduce temperature differences that cause condensation.
• Use Mats or Carpeting with Proper Underlay: If you have mats or rugs on concrete floors, ensure they are breathable and have moisture-resistant underlays to prevent condensation from being trapped.
• Use Humidity Sensors: Install a hygrometer in areas like basements and crawl spaces to monitor moisture levels regularly.
• Run Air Conditioners: Air conditioners help reduce humidity levels during warm weather, preventing mold growth on concrete.
• Check Concrete Cracks: Inspect for cracks in concrete walls, floors, or slabs and seal them to prevent moisture entry.
• Trim Plants Around the Foundation: Keep shrubs and plants away from the foundation to reduce moisture retention near concrete walls and slabs and ensure the root structures don’t degrade the material.
• Clear Debris Regularly: Ensure leaves, soil, and other debris are removed from concrete surfaces, especially patios, walkways, or driveways, as they can trap moisture.
• Run Air Purifiers: These machines will remove particles like mold spores and bacteria, reducing the risk of growth developing.

That’s a lot of information! Don’t try to tackle every step at once. Pick one step at a time, and knock them out when you can. Evey action you take to prevent issues like mold on concrete is a huge positive towards keeping your home healthy.

Final Thoughts

While concrete may seem like a solid and easy-to-maintain surface, it’s not indestructible! Mold can turn the surface and your home into a serious health hazard for you and your family. Microbial growth can also mess with the structural integrity of the surface, leading to further hazards in your home. 

Knowing how to handle mold on concrete properly should it pop up and how to prevent it (most importantly) is an extra layer of protection for your indoor environment and wellness.