Mold fungus and mildew image

Signs of mold in a basement are quite easy to detect. But sometimes it takes a keen eye to notice them and their potential health risks.

Mold is a fungus that produces toxins, which can be poisonous. Some varieties have been reported to cause respiratory issues, headaches, diarrhea, and more.

Asides your health being at risk, mold is destructive to drywall, furniture, ceiling, and flooring. 

According to the EPA and CDC, here a few signs of mold in your basement:

The musty smell

It’s easy to miss the visible growth of mold in your basement; however, what you cannot miss is the smell.

Of course, basements don’t get the most ventilation in the house. However, the rusty and dank odor of mold should be noticed.

The funky smell of old is more prominent when you have moisture leaks in your basement. 

Molds produce strong smells and unpleasant smell, and inhaling these odors have been shown to cause nausea, dizziness, fatigue, nasal irritation and headaches. 

Also, if the heating or air conditioning in your basement is starting to smell musty, this is a subtle sign of mold. Air conditioning units especially are ripe spaces for mold growth. 

And if your basement smells no matter how many times you have “cleaned” it, this could be mold. The stronger the smell from the basement or one corner of the basement, the more likely the culprit is mold.

Spotted basement walls, floors, and ceiling

The obvious sign of mold problem in your basement is mold growing out on the basement walls, floors, and ceiling.

Mold can come in several colors, textures, and shapes.

When you start noticing strange particles stuck to surfaces in your basement—perhaps slimy green or fuzzy grey—acting fast to prevent further growth should be your immediate concern.

Triggers asthma and allergies 



Asthma disease concept.

Mold spores are capable of entering the lungs and triggering asthmatic reactions.

This study states one in five cases of asthma in the U.S. can be traced to mold. If your asthma is triggered in the basement, or you experience difficulty breathing, coughing, chest colds, running nose, wheezing and sneezing in the basement, you may have a mold problem.

In moldy houses, infants and children are even more vulnerable in asthmatic attacks. Moreover, for people with pre-existing respiratory problems, the symptoms are flared up in a moldy home. 

You might need to start testing for mold if you experience chronic, persistent cough whenever you enter the basement and your seasonal allergies flare up consistently. If the symptoms are persistent and occur quickly after you finish doing laundry in the basement.

Watery and itchy eyes

If your eyes sting or get watery when you go down to the basement, it’s possible you are allergic to mold which has infected your house.

The symptoms may include nasal congestion and coughing triggered by old spores. And according to the American College of Allergy, Asthma & Immunology, it is recommended you study (for 14 days) your reactions and see if they are triggered when you step in certain spaces of your building.

Getting exhausted often

Toxic mold can cause several health problems, and fatigue is one of them. If you find yourself getting tired for no reason, the mold in your basement could be the cause of the problem.

Skin problems

Another sign of mold problem is when your skin feels scaly, dry and itchy after visiting the basement. This could be a tingling, burning or itching sensation racking up your skin as it comes in contact to mold or mold spores.

If you keep clothing close to the basement and feel itchy whenever you wear them, you may also have a mold problem. 

Bubbling paints on basement walls

While bubbling paint on walls may not directly prove the presence of mold, bubbling paint could mean there is a moisture problem in your basement, which is often a precursor to a mold problem.

Finding the source of the moisture, waterproofing your basement, scraping, drying, and then repainting are necessary steps for such a scenario. 

Peeling wallpaper

If the wallpaper in your basement wall begins to crack, you may have a moisture problem, which is a precursor to a mold problem.

Of course, wallpaper is expected to get scruffy or discolored over time; however, when the wallpaper begins to peel off or abnormally bubbles or cracks, this means your basement walls are damp. 

Squishy basement floors 

No matter the type of flooring you have in our basement, a squishy floor is not a good sign. The softness of the flooring shows that it is damp and ripe for mold contamination. And if the floor wood begins to rot, it needs to be changed to prevent further damage.

Lumpy insulation

Examine the insulation in our attic. If you notice lumps across the surface, you could have a moisture problem, which could lead to potential mold issues.

When water enters your insulation and drywall, it creates the right condition for them to grow within the walls.

This kind of mold growth is quite dangerous because they are hard to detect as they located in the interior of the basement wall.

Flooded basement

When your basement gets flooded, preparing for a mold attack is the smartest thing you can do. And it doesn’t even have to be a large flood; small amounts of water seeping into your basement can create the perfect conditions for mold to thrive.

DIY or call a professional?

diy repair or call a professional

Diy repair or call a professional


If you spot signs of mold in your house, treat the problem as soon as possible.

A little DIY can solve the problem.

You might not need to purchase a mold testing kit or perform mold testing if the mold is visible. As long as you can smell it or see it, it must be eliminated as soon as possible, no matter the type of mold it is.

For small moldy spaces not more than 3 square feet, a DIY cleanup can be effective.

Of course, you would have to wear an N-95 respirator, gloves, and protective eyewear during the process of DIY remediation.

This starts with stopping the leaks, cleaning up the moisture, and then scrubbing off the mold with an antifungal solution (e.g. bleach solution).

But in cases where you cannot smell or see mold but suspect it is hidden—due to water damage beneath your basement floor or behind the basement wall—an experienced professional can help trace the source.

If the moldy area is more than 3 square feet, calling a certified professional is vital. 

Some mold remediation professionals can even help test the mold to know its species and the likely health risks it can cause you and your family.

Final note

Mold is easy to spot but very resilient, and you may never absolutely kill them off. However, you can stop mold accumulation by preventing leaks or waterproofing your basement.

Since mold spores need water to thrive, keeping the air dry is necessary. 

  1. Hi Bob, Thanks for the information. Very recognisable: our basement/garage is also suffering form bubbly paint areas. It’s a rental house and every year the landlord comes to “solve the problem”. Wet areas are being scratched off, and wals are getting repainted. Of course this is not a solution, but our house is an old house with single walls and not the best moist insulation. And landlord cannot do much more he says. So we will have to live with it. During summer things are much beter as the weather and air is dryer and we can sometimes leave the garage door opened for a fresh breeze. The problems return in autumn and winter. It is what it is I guess. Luckily the rest of the house is mold-free.

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