Mold On Floors - How to Handle It Step-by-Step

By: Licensed Mold Assessor Brad Fishbein

January 18, 2023

Having mold on floors can be an eye sore but it can also be potentially dangerous. Depending on the material the floor is made of, certain types of mold can grow that can cause mycotoxins. The cause of the mold which is water is crucial in determining how bad mold on floors is and how to fix it.

But how can water get under the floor? And if the mold is bad on the floor itself, what does the mold look like underneath?

In this article, we are going to investigate everything you need to know about mold on floors including:

  • What are the causes of water under flooring material
  • The different types of floor mold grow on
  • How to remove mold on flooring
  • Is Mold on the Floor Dangerous
  • How to Prevent Mold on Floors
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Causes of Mold on the Floor

Mold is a type of fungus that can grow on any surface that is damp and dark. Floors are particularly vulnerable to mold growth due to their frequent contact with water, making them an ideal breeding ground for mold infestation.

There are several common causes of mold on floors.

Water Damage

The obvious cause of mold on floors is water damage. Water damage can cause mold on floors but more likely will cause mold to grow underneath floors. There are multiple causes of water damage including:

  • Plumbing leaks
  • Window leaks
  • Cracks on the exterior
  • Roof leaks
  • Slab leaks

When moisture accumulates in areas such as around baseboards (where black mold can grow behind) or floor covering, it creates an environment where mold can thrive. If there is some kind of moisture barrier, the water damage could be worse than originally thought, and it could possibly be the entire floor.

High Humidity Levels

High humidity levels create conditions conducive to mold growth because moisture remains in the air longer than normal when there is excessive humidity present indoors.

High humidity levels will typically only cause surface mold on floors however if you have a wooden floor it can cause deterioration and damage to the floor itself.

The Types of Floors Mold Grows On

Determining how big of a mold problem you have largely depends on what type of flooring you have. Here is a list of the most common types of floor covering in a home and how susceptible mold damage is. People tend to get caught up with black mold which is one type of mold called Stachybotrys on the floor, but there are other types of mold to be concerned with.


Real Hardwood Flooring- There is a misconception that some of the floors we will cover in this section such as laminate wood flooring are actually completely real wood which is untrue. But a hardwood floor made of real wood is actually 100% wood flooring. Depending on how a home is built, the floor may be on floor joists or a concrete slab. A hardwood floor is very durable but with the right amount of water can certainly support mold growth. The most common type of mold found on wood floors is a type of mold called Chaetomium which can produce mycotoxins.

Laminate Floors- As stated above, laminate flooring is not real wood floors. It is basically a fiberboard with an image of wood on top. Talk about fake news! Laminate flooring gets damaged much easier than real wood flooring. There is commonly plastic sheeting under the floor which can retain moisture. Multiple different species of mold growing underneath laminate flooring is very common

Engineered Wood Flooring - If hardwood flooring is the upper-end flooring and laminate is on the lower end, then engineered wood floors are in the middle. They can often be mistaken for hardwood floors. There is hardwood on the top of wooden floorboards that are typically made of high-end plywood. Because they are wood, just not 100% real hardwood doesn't change the fact the material can support microbial growth.

Carpet Flooring- The carpet is really great to walk on but this product which is mostly made of synthetic fiber, is a breeding ground for mold growth. Because it's so porous, when it gets wet it can cause an extremely musty smell. All different types of mold can grow in carpets and because the mold spores are so tiny, even a HEPA vacuum can't always get rid of them. Also included in carpet flooring is mold on a carpet pad and mold on tack strips which is part of the carpet flooring system.


Vinyl Flooring- Luxury Vinyl flooring has become more popular in recent years and has been an excellent replacement for laminate flooring as it's almost as affordable. Vinyl floor can be mold resistant and built to withstand water damage. Mold does not typically grow on Vinyl floors very easily.

Epoxy Flooring- Epoxy flooring is commonly found in Garages and some commercial spaces. Epoxy flooring is not porous so mold will not grow on it.

Concrete Flooring- Concrete is semi-porous and can support some mold growth. While the mold growth won't typically produce mycotoxins it certainly is a concern and can cause a musty smell.

Tile Flooring- Mold only uses organic material as a food source. Tile flooring is non-organic and does not support mold growth. However, mold can grow on the quick-set compound underneath the tile.

Marble Flooring- Marble is stone so it is porous. Mold can grow under the right conditions but will not typically produce mycotoxins.

Subflooring- Subflooring is the plywood underneath the floor covering. Subfloors can be on the 1st or 2nd floor of the home and is essential to the structure of the home. So what happens if you have mold on the subfloor? Well, in some cases, part of the subfloor can be removed however in other cases it can be a structural issue and will need to be left in place and sanitized. A bigger issue is if there is wood rot on the subfloor which can be worrisome structurally.


Even though mold thrives on some of the materials more than others, All these types of materials have one thing in common: Mold can grow on the surface.

Be Aware of Floating Floors

Floating floor systems involve floorboards that are not glued to the ground. They are locked into each other like a puzzle. Usually, vinyl or laminate is used for these types of flooring systems.

Here's the concern about these type of floor systems:

Because the floor is lifted off the concrete slab, it's hard to detect water under it. If the floor starts to lift, it could be a sign of water underneath and should not be ignored.

How to Remove Mold from Flooring

Mold can spread quickly with any kind of leak issue. You need to be prepared that if there is mold bleeding through the floor on the backside the floor that will be even more mold growth. This holds especially true if there is a crawl space.

Obviously, the cause of the leak will need to be corrected before the moldy areas are removed. Mold removal on the floor needs to be done with something called a containment barrier. A containment barrier involves putting an area under negative air pressure and ensuring the mold spores don't cross-contaminate from one area of the home to another.

Here are the important questions that must be asked in determining how to remove mold from flooring:

  1. What is the cause of the mold?

  2. If there is a leak, is it new or old?

  3. What drying process if any needs to be applied?

  4. Do the affected surfaces need to be cleaned or removed?

  5. Is it surface mold or is there mold under the floor?

  6. Is the entire room affected or just one area?

All these things need to be considered because it's not a one size fits all section. You may need to bring in a professional to do the job. If the subject area is larger than 10 sq feet it is recommended by the EPA that you bring in a professional to do the job. If the leak has been going on for a long time black mold may be present under the floor as well. If it's something that you decide is a DIY job, safety precautions need to be taken which can include protective clothing and an OSHA-approved particle mask.


Here are the processes if mold is just on the surface and can be cleaned:

Clean the Floor with Detergent and Water

The first step in removing mold from your floor is to clean it with detergent and water. Start by using a vacuum cleaner to clean up any loose dirt or debris that may have accumulated on the surface of the floor. Then mix one cup of detergent per gallon of warm water in a bucket and use a mop or sponge to scrub the affected area until all visible signs of mold are gone. Be sure to rinse off any remaining soap residue that the cleaning solution leaves behind before allowing the area to dry completely.

Use a Fresh Borax Solution for Stubborn Mold Stains

If you find that some stubborn stains remain after cleaning with detergent and water, then you may need to use a borax solution as an additional measure against mold growth. Mix one part bleach with four parts water in a spray bottle, then spray directly onto the affected areas until they’re saturated but not dripping wet. Allow this solution to sit for at least 15 minutes before rinsing thoroughly with clean water and drying completely using towels or fans if necessary. If the borax solution isn't efficient, there are other solutions you can try. Be careful using borax on hardwood floors.

Apply Vinegar Solution To Kill the Remaining Spores

Once you’ve removed all visible signs of mold from your floors, it is important to kill any remaining spores that could cause future problems. There are biodegradable solutions that are non-toxic. But another way to do this is, to mix equal parts white vinegar and warm water into a spray bottle and apply liberally over affected areas until they are damp but not soaking wet (do not rinse). The acidity of the vinegar will help kill off any lingering spores while also helping prevent future outbreaks by inhibiting their growth within your home environment overall. The vinegar solution can also help clean excess solution or borax residue.

Removing mold from the flooring is an important step to take in order to maintain a healthy home.

Professional Remediation Services

Professional remediation services are experienced in identifying and removing mold safely and effectively. If you decide to go the route of a professional mold abatement professional to remove mold-damaged flooring, these are the steps they will take.

Identifying the Source of Mold Growth

Professional remediation services have the expertise to identify where mold is growing and why it’s there. They use specialized equipment such as moisture meters, infrared cameras, hygrometers, and air sampling devices to detect hidden sources of water that may be causing mold growth. By accurately pinpointing the source of the problem, they can then provide effective solutions for eliminating it.

Removing Mold Safely & Effectively

Once they’ve identified where the mold is coming from, professional remediation services will use appropriate techniques for removing it safely and effectively. This may include using HEPA vacuums or wet-vacuuming with an anti-microbial solution; sealing off affected areas; applying fungicides; or replacing contaminated materials such as drywall or insulation if necessary. The goal is always to ensure that all traces of mold are eliminated so your home remains safe and healthy for you and your family.

Is Mold On Floors Dangerous?

The mycotoxins that water-damaged floors can lead to can be dangerous. There are health risks associated with mycotoxins. In some cases that can be severe reactions. Be aware though that just because you have water damage under the floor doesn't mean the mold spores or gasses the water-damaged material lets off are affecting you.

Sometimes the microbial growth is under the floor only and doesn't become aerosolized until the floor is removed. That is why it's crucial if it's suspected there has been water damage under the flooring for a while, it's best to leave the job to the professionals, especially if the job involves removing wood flooring.


Preventing Mold on Floors

To prevent mold growth on the floor, homeowners should take several proactive measures.

First and foremost, any plumbing leaks should be fixed immediately to keep your home dry. Additionally, dehumidifiers can help reduce humidity levels in damp areas of the house such as basements or bathrooms. Proper ventilation is also key; make sure that moisture-prone areas are properly ventilated to allow air circulation and discourage mold growth. If possible, use exhaust fans when showering or cooking to remove excess moisture from the air quickly and efficiently.

It’s also important to regularly inspect your floors for signs of water damage or discoloration that could indicate an underlying issue with mold growth. In particular, hardwood floors may need extra attention since they can easily absorb moisture if not sealed correctly—so check them periodically for any warping or soft spots that might suggest a problem below the surface. It’s best to address these issues before they become more serious so you don’t have to deal with extensive repairs down the line.

Finally, regular cleaning will go a long way toward preventing mold buildup on your floors. Sweep up dirt and debris often (especially near entryways) and mop regularly using warm water mixed with detergent or vinegar solution (depending on what type of flooring you have). This will help get rid of spores before they spread further throughout your home, giving you peace of mind knowing that everything is clean and safe.

Taking preventive measures to keep your floors free from mold is essential for maintaining a healthy home. Knowing when and how to seek professional help can be the difference between living in an unhealthy environment and a safe one.

Meet the author: Brad Fishbein is an ACAC council-certified Microbial Investigator. In the fall of 2012, he became a Licensed Mold Assessor in the State of Florida through the Department of Business & Professional Regulation. Brad has helped homeowners with over 5,000 successfully completed Mold Inspections since 2009.

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