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Can Mold Grow on Concrete

By February 10, 2021Home maintenance
Can mold grow on concrete

Mold can be harmful to people and their health if it is not taken care of right away.  We know that mold can grow on surfaces in the home and sometimes we see it on plants, but can mold grow on concrete? 

Sure!  Mold can grow anywhere the spores land.  You may not think there is nourishment on the concrete for it to grow but there are other factors that indeed help it to grow.  Unfortunately, it can deteriorate the concrete and the stability and even allow bacteria in. 

Let’s take a look at why this is important, what makes mold grow on concrete, what makes the mold grow on concrete, ground water intrusion, installing drains,            

Why This is Important

Mold growth is essential for breaking down organic material in the environment.  There are thousands of different types and mold can settle on the ground, objects, dead trees, building surfaces etc. It grows where it has oxygen and also temperatures between 40 degrees and 120 degrees. 

Mold will become dormant in colder temperatures.  However, one of the bad things about mold is it can also cause health issues in many people so it needs to be taken care of.  In addition, it grows on concrete and can cause structural issues.

What Makes Mold Grow on Concrete

Mold spores land on the concrete and then the dust, algae, bacteria, and other particles allow the concrete to feed on them and produce the mold. Next, the mold starts to wear away at the concrete, causing it to degrade. It becomes porous and allows more moisture and intrusion. 

Unfortunately, concrete loves water and absorbs it like a sponge allowing mold to grow in the right setting.  It can also grow after the concrete slabs were poured and they didn’t have a good moisture barrier. The mold can also grow if the slab wasn’t allowed time to dry when it was poured.

Additionally, mold can be found outside on concrete in an area that is in the shade, damp, and does not get a lot of sun or heat.

Mold or Efflorescence

Mold can be in many colors, black, white, etc. The black mold is easy to identify. However, the white mold and efflorescence look a lot alike.  What is efflorescence?  It is a crystalline growth that occurs when moisture moves through concrete. 

In this process, the minerals get pulled along with the water and then leave behind the salts and minerals as the water evaporates. How can you tell?  Spray water on the white moldy surface.  If the mold goes away, then it is efflorescence and not mold. 

Main Culprit: Ground Water Intrusion Causes Mold to Grow on Concrete
Eaves and downspouts help with flow of water

Main Culprit: Ground Water Intrusion Causes Mold to Grow on Concrete

Look at the foundation of your home or the basement from the outside.  Do you have any cracks in the foundation? If yes, you will want to have an inspection.

Perhaps you are noticing that water is pooling near the home?  If you are finding mold in your basement, this could be the culprit. If you are not seeing the mold yet, this is a warning sign that it may happen soon.

Make sure you have gutters installed so they can direct the flow of water off the house and into specific areas.  This is where installing downspouts is a great idea to get the water 4-10 feet away from the home. 

Does the ground look level?  If not, grading it would be a great idea so the slope is away from the home and not towards the home.  Keeping water away from the concrete of the home is the idea. If not, it seeps into the home and combined with the moisture, will create mold.

Installing a French Drain or Interior Drain Might Be a Good Solution

If the ideas above don’t work, then installing a French drain or interior footing drain to help with the water is the way to go. 

French drain
French drain

French Drain

A trench that has a perforated pipe with gravel and allows the water to drain from the yard. This can be a DIY or you can call a professional.  An exterior French drain is about $1000-1500 and is less if installed while the home is in the building process.

Interior Drain

The interior drain is installed in the basement to direct groundwater to the sump pump and away from the home.  If installed while the home is in the construction process, it is about $1500 to $2000 extra

If it is installed after construction, it can be about $7,000 or more depending on the size of the basement. The reason it costs so much is it will require concrete to be broken and a jackhammer to be used to get through the floor.

Humidity Causes Mold to Grow on Concrete

Mold Related to Humidity

If the mold on the concrete is not due to ground water intrusion, then check the humidity in the basement.

Lower the Relative Humidity

In a basement that does not have good ventilation, mold can grow due to moisture in the air that lands on the surface.  Make the room warmer and this should help make the concrete in the wall warmer, thus not allowing the mold to grow.

However, if the relative humidity remains at 60% or below it is fine.  If it goes above that, then mold will grow.

Improve ventilation

Improve Ventilation

You can improve ventilation by using floor fans, dehumidifiers, or exhaust fans in the basement.

Mold Inspection

Call a professional to do a mold inspection.  They are trained in this area and can suggest if you need drains, fix the grading, ventilation, lowering the humidity, or something else.  In addition, they can help with getting rid of the mold and it hopefully not coming back.

How to Remove the Mold

Getting rid of mold can be difficult and you can try to do it on your own if it is a 3ft x 3ft square.  Some people will recommend using bleach, but a concoction of ½ vinegar and ½ baking soda in a spray bottle is a good idea to try first. 

If this doesn’t work, you can try bleach or contact a professional.  Remember any time you are working with mold, make sure you are using protective gear.

Mold on carpet
Mold on carpet

Mold on Carpet

Are you finding mold on the carpet near the concrete?  If yes, you can use baking soda to try to remove it. Do this by putting some on the mold and letting it soak overnight. 

This will allow the mold to soak up the moisture and odor.  Then, add a little bit of white vinegar to the surface and scrub it to see if you can get it out.  If not, you can cut out the piece and leave a 12-inch border, and put a replacement piece on the carpet.

Future Prevention of Mold

  1. Put plastic covering over basement windows so groundwater does not get in.
  2. Check the window in the basement to see if it leaks when it rains.
  3. Also, don’t store papers, firewood, and other materials that mold likes to grow on in the basement.
  4. Install or clean out gutters, as mentioned above.
  5. Add eaves and downspouts to the home.
  6. Use a sealant on the concrete to try to stop the mold growth.

Selling or Buying a Home With Mold Growing on Concrete Issue

If you are selling or planning to buy a home with mold on the concrete, it does present a safety issue and will come up in the home inspection.  Taking care of the mold is essential and needs to be done. 

When to Call a Professional

Call a professional if you need help with the mold on the concrete and finding the source.  The professional can help figure this out for you and give you suggestions or recommend someone to treat the spots. Also, if you have a large area, they can take care of it.


Mold really does grow on concrete inside or outside the home. If you notice it is growing and you don’t want to take care of it yourself, contact a professional. 

Finally, mold can be difficult to take care of and professionals are there to help and to answer your questions.  Leave us a reply below or contact us if we can help you!

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