Black Mold in Basement: Is it Dangerous & How to Remove it

Black Mold

As you head down to your basement you smell a strange, earthy odor that you hadn’t noticed in the past. You take a quick look around and discover a black, fuzzy substance growing on the wall, or maybe on some cardboard boxes that you have been storing down there. What you have discovered is that you have a mold problem. When you find mold, especially black mold, in your basement there are several questions that come to mind:

(1) Is it, or can it be dangerous?

(2) How did it get there?

(3) How can it be removed safely and completely?

(4) Do I need to bring in a professional to do the work?

(5) How do I keep it from coming back?

What Is Mold?

You need to understand this, mold is an organism, not dust or dirt! The word “mold” is a non-scientific term that generally refers to fungi with a fuzzy, hairy, or powdery appearance. It cannot be eliminated with ordinary household detergents or cleaning solutions. Mold is found everywhere in nature, and that is a good thing.

The main job of mold is to cause decay and decomposition. Can you image the depth of the mess we would be in if things didn’t decompose. There would be no oil deposits and we would be up to our necks in dead dinosaurs and plants.

There are many instances in which the existence of mold is a good thing? Many of our modern medicines are developed through the use of fungal chemicals, medicines like penicillin, lovastatin (used to lower cholesterol), and cyclosporine (administered after an organ transplant to help prevent the rejection of the organ). And then there is food! Think of stuffed mushrooms, most blue cheeses, hard salami, and dry-cured county ham. Yes, mold can be a good thing… unless we have large amounts of the black stuff growing in our basements.

Common Places You May Discover Black Mold in Your Basement

Mold needs moisture, warm to moderate temperatures, an organic food source, and poor ventilation (a lack of air movement) to begin to grow and develop. In the typical basement there are many areas that are prone to mold growth. Mold infestations can be a result of water leaks of any kind obviously, but condensation and higher than normal humidity can also result in a mold problem. Potentially high-risk areas may include:

  • Around windows or vents
  • Around pipes and ductwork
  • In areas near a sump pump
  • Near foundation leaks

What Is “Toxic Black Mold” and What Does It Look Like?

The color of mold has very little to do with how dangerous it may be. And yet not every black mold is toxic. Can you visually determine if the mold in question is in fact stachybotrys chartarum just by looking at it? The answer is sometimes yes… but usually no.  For a mold expert, it is fairly easy to identify black toxic mold; for the untrained eye, the answer is usually no. That said, you have probably read about “Toxic Black Mold” in the media or heard about it on the news. Stachybotrys Chartarum is the species of mold that people are usually referring to when they are talking about “toxic black mold”. This species stands out from the rest as it can release spores and mycotoxins into an indoor environment, which can lead to some serious health complications. Stachybotrys is a slow growing mold, requiring large, continuous amounts of moisture. It is usually black to dark brown or greenish-black in color depending on the stage of its growth and it will be slimy to the touch.

Other Common Types of Black Mold

There are several different types of black mold. While Stachybotrys is the most infamous, other types include cladosporium, penicillium, and fusarium. Cladosporium is a very common mold found both indoors and out. It can appear olive-green to brown or black in color. Penicillium mold is usually blue-green or dark brown and should be considered a health risk. Fusarium is lighter in color, usually reddish-violet to purple.

Black Mold vs. Mildew

Is it black mold or is it mildew and what’s the difference? They are similar yet distinct and they are both members of the fungi family. The main difference between mold and mildew is that mold has a fungal structure, or roots. Mold will penetrate almost any organic material it grows on and eventually damage (decay) the structural integrity of the material. Having a root system means that mold is more difficult to remove completely.

Mildew, on the other hand, is a surface fungus. It only grows on the surface of materials, which makes it much easier to eliminate. It usually starts as a white, powdery substance that may darken over time.

What Causes Black Mold?

Some of the more common reasons for mold in your basement have to do with unwanted or uncontrolled water:

  • This water can be the result of a broken pipe, a faulty sump pump, a leaky water heater, or possibly foundation cracks.
  • Condensation on exposed plumbing pipes or concrete floors during warmer summer months. Or maybe the basement windows have older, single-pane glass that allows condensation to occur due to inside to outside temperature differentials.
  • HVAC systems have a condensation drain to remove water that is collected from the processed air. If this drain develops a clog, the water has the potential to flood your basement in a relatively short amount of time. Many HVAC systems have a whole-house humidifier as part of the system. The unit may be set too high, increasing the basement’s humidity above 50 percent.
  • Dryer vents that are not vented or not properly vented to the outside.
  • Ground water that is not directed away from the foundation. Things such as improper grading, downspouts not being extended out far enough, or gutters that are clogged or pulled loose from the fascia boards, allowing rainwater to collect around the foundation, can result in a mold issue.

Is Black Mold in Your Basement Dangerous?

Media stories and lawsuits have made homeowners more aware of the dangers of “toxic black mold”. People often mistakenly assume any black mold is toxic mold. The truth is, the mold itself isn’t necessarily toxic, but the compounds it produces, called mycotoxins, are. If you come into direct contact with these mycotoxins, or inhale the mold’s spores, you can become sick. 

Exposure to black mold can cause numerous health problems. The toxins tend to cause suppression of the exposed person’s immune system. These health problems may include:

  • difficulty breathing
  • sneezing
  • coughing
  • sore throats
  • itchy and watery eyes
  • asthma attacks
  • chronic sinus infections
  • depression and fatigue.

Symptoms can range in severity from mild to very severe. Extended exposure to Stachybotrys can eventually result in bleeding in the lungs and damage to the liver and kidneys.

The danger of black mold in homes is the greatest for infants and children, elderly people, pregnant women, and those with pre-existing health problems like asthma, cystic fibrosis, other respiratory problems, and disorders of the immune system. An additional group who needs to stay away from black mold exposure is patients who are undergoing chemotherapy treatment. Chemotherapy is designed to weaken a person’s immune system, which in turn weakens their resistance to mold. The truth is exposure to black mold can make anyone sick, including healthy adults. Even your pets are not exempt from the health dangers of exposure to stachybotrys chartarum.

How to Get Rid of Black Mold in Your Basement

The first step in getting rid of black mold, or any mold, is to eliminate any leaks or water intrusions that allowed the mold to develop. Second, any and all indications of the black mold must be completely removed from the home. Mold often grows in hidden places; there is always more mold present than you can see with the naked eye. Mold will grow inside walls, under flooring, above ceiling tiles, inside HVAC systems, and inside cabinets. It is critical to remove all traces of black mold because if you miss even a little bit, the mold will return once any uncontained moisture is reintroduced into your basement. 

It is virtually impossible to completely remove mold from porous surfaces, especially drywall or carpet cushion. Porous materials need to be cut out, double-bagged, and removed from the home. If wood materials cannot be completely removed due to structural concerns, like wall studs or beams, they must be cleaned and then sealed by a process of encapsulation, a permanent covering (sealing) of the contaminated material. Other non-porous materials, like metal, ceramic tile, laminate or stone countertops, and concrete can be successfully cleaned without complete removal.

Even the slightest disruption of mold can cause the dispersal of mold spores, making them airborne. This can allow mold spores to spread to other previously unaffected areas of the home. Strict safety procedures must be followed in order to avoid making your mold problem worse by the spreading mold spores. Containment chambers should be erected to isolate affected areas and negative air machines put in place to help filter mold spores out of the air.

Mold removal can be complicated, especially when dealing with large amounts of mold and it is often times best left to professional remediators. You should only attempt mold removal yourself if it covers less than ten square feet.

A common misconception is that you can successfully remove mold with chlorine bleach. Chlorine bleach is extremely effective at killing bacteria, but not mold. Bleach is composed of chlorine (4%) and water (96%). The chlorine will not penetrate any surface; it will possibly only kill what is on the affected surface. The water in the bleach will penetrate, doing more harm than good by providing a source of moisture to the mold’s roots. 

How to Prevent Black Mold in Your Basement

Mold and mold spores are everywhere and molds have been present on Earth for millions of years. Just like every other living organism, mold needs water to survive. Controlling humidity and moisture are the most important factors in preventing basement black mold growth. Constantly be on the lookout for water leaks of any kind. Keep an eye on humidity levels in the basement and consider purchasing and operating a residential dehumidifier in the basement to help further control excess humidity.

Try not to store too much “stuff” in your basement. Excessive clutter will restrict airflow and affect ventilation. When you do store things in the basement (and who doesn’t), keep them up off of the floor and away from outside concrete walls. Avoid storing paper or cardboard if at all possible, as these materials are much more prone to absorb humidity and are some of mold’s favorite food sources.

Insulate exposed cold water pipes and metal ducting to reduce the chance of condensation.

The Cost of Basement Black Mold Removal

What cost might you incur for black mold removal from your basement? What factors may affect the cost? The factors that have the most influence on cost are the size of the affected area, the location, and the severity of the damage. 

For size, you should think in terms of square footage. On average the sq. ft. price can range from $10 to $25. A 10’ x 10’ room (100 sq. ft.) will cost between $1,000 and $2,500.

Location and severity go hand in hand. The more difficult the location (in an attic or behind kitchen cabinets for example) and the amount of mold present may increase the average cost you can expect to be charged.

The costs mentioned are for the physical mold removal only. The cost of replacing materials and finishes that required removal are not included.

Should You Remove Black Mold Yourself?

You should never attempt to “kill” or “cover up” mold. Mold needs to be removed. The EPA suggests that when a mold-affected area is less than 10 square feet it is possible for homeowners to do it themselves. This is a very risky suggestion. Here’s why:

1. Your health and your family’s health. Mold has the potential to cause health problems. Molds produce allergens that can cause severe health reactions in sensitive individuals. These allergens may not affect you, but may affect other members of your family. Reactions to mold exposure can be immediate or delayed.

2. Personal protective equipment is required. The PPE needed includes disposable clothing like a Tyvek suit with a hood, gloves, shoe covers, and a N-95 rated full-face respirator. Before you attempt to work in a full-face respirator, you should be checked by a qualified healthcare professional to ensure that it is safe for you to do so.

3. Containment is critical. The contaminated area(s) must be sealed off from unaffected areas of the home. Containment involves more than just closing the door to the affected area. All openings need to be sealed with sheets of heavy plastic and duct tape. This includes HVAC vent openings.

4. Negative air pressure in affected areas needs to be established. By placing the affected area(s) under negative pressure, air will flow into the area and keep airborne mold spores from escaping into the remainder of the home. Too much negative pressure can be just as dangerous as too little. Too much can cause exhaust gases like carbon monoxide to flow into the work area.

5. Removal and cleaning and/or encapsulation protocols must be followed precisely. Contaminated materials must be removed, bagged, and disposed of according to local regulations. Cleaning the affected area(s) needs to be completed more than once and done over multiple days. This will ensure that all of the mold and mold spores have been collected and removed.

Only after all of the above steps have been completed, and the results confirmed by testing, should repair and replacement be done. Safe and successful black mold remediation is a complicated process that, for the most part, is best left to a professional.

Mark Huey

Mark Huey is an IICRC-certified master remediation technician. He founded & operated an independent water damage restoration business for 21 years. He has written blog articles, web-content, and developed Powerpoint presentations on all types water damage and mold remediation issues.

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