With its light color and unprecedented durability, concrete is a great material of choice for patios, driveways, walks, and basement walls and floors. And while concrete is one of the strongest raw construction materials, its porous consistency makes it susceptible to mold, which takes root in the moisture trapped in those tiny nooks and crannies.
Once it’s taken root, it grows and spreads, marring your beautiful patio or driveway with black or green splotches that aren’t only unsightly but also present a potentially serious health hazard.
Knowing how to remove mold from concrete effectively is key to maintaining the aesthetics and safety of the concrete in and around your home. The best way to remove mold from concrete is to apply a bleach solution, laundry detergent, and water to the affected area, scrub it with a brush, and rinse it clean with a sponge indoors, or hose or power washer if outside.
In this article, we’ll examine why mold forms on concrete, to begin with, review the best methods for cleaning mold off of concrete, and discuss strategies for ensuring the mold doesn’t return.
- Can Mold Grow on Concrete?
- Is Mold on Concrete Dangerous?
- How to Remove Mold From Concrete: Options
- How Do You Prevent Mold From Growing On Concrete?
- How to Get Rid Of Mold on Concrete Basement Walls and Floor
- How to Remove Mold From Concrete Patio
- Safety Considerations
Can Mold Grow on Concrete?
Mold can indeed grow on concrete. This typically occurs on shady areas of driveways, patios, and steps that get wet but take a long time to dry because they don’t receive a lot of direct sunlight.
This includes the north-facing side of a wall, concrete in shady areas, and floors covered by a patio. These dark, damp areas give mold and mildew a chance to breed and grow.
Indoors, mold can grow in places where condensation collects or as a result of leaky pipes or rainwater that seeps in through a foundation.
And since concrete is porous, it’s an excellent environment for mold growth. Mold growth in concrete is especially prevalent in regions that experience hot, humid weather.
When mold grows on concrete, it typically looks like black or green splotches. Mold can also be white; however, this is often confused with efflorescence, which is salt build-up on concrete caused when water evaporates into the porous surface of the concrete, leaving the salt that was in the water behind.
Is Mold on Concrete Dangerous?
While mold on the exterior of a home can be unsightly, mold growing on concrete surfaces in the home interior can be a dangerous health hazard. Black mold can cause serious health problems and must be dealt with as soon as it is detected inside the home.
Black mold can aggravate allergies, cause asthma attacks and irritate the eyes, nose, and throat. If left unchecked, it can also cause significant property damage, especially if it spreads beyond concrete to the wood construction.
If removing mold from indoor space, it’s important to use protective gear. Extensive mold problems discovered indoors require expensive mold mitigation efforts from licensed professionals.
How to Remove Mold From Concrete: Options
1. Liquid Laundry Detergent and Household BleachOne of the most common and effective means of removing black or green mold from concrete is bleach. Bleach will kill mold down to the root, cleaning it off concrete while also preventing it from returning.
To clean mold off concrete, begin by cleaning the concrete surface with a hose, removing as much black mold as possible. If the concrete is located indoors, use a sponge to scrub away the mold. A scraper is also an effective tool for removing the mold from concrete.
Keep in mind that though these methods are effective, physically scrubbing or scraping the mold away will not remove the root, which is embedded inside the porous concrete. If the root is still intact, the mold will simply grow back.
Killing mold beneath the concrete’s surface requires cleaners that can penetrate the concrete. While bleach is effective and kills mold, its surface tension does not make it ideal for soaking concrete. Laundry detergent is a better option.
Create a cleaning solution by mixing a cup of laundry detergent with a gallon of water. Use a sponge or brush to apply the solution to the floor. The detergent will soak into the concrete’s pores, killing the black mold’s roots.
Use a scrub brush to ensure the solution penetrates the concrete and to remove the mold’s roots. When complete, rinse off the concrete with clean water. If outdoors, use a hose. If inside, use a mop.
Repeat this process if any mold is still present. Dry the concrete with a fan until it is completely dry.
Next, create a bleach solution by mixing a cup of bleach with a gallon of water. Use a spray bottle to apply the solution to the concrete and allow it to dry. The bleach will serve as a shield to prevent new mold spores from taking root.
2. White VinegarIf you don’t have bleach on hand or look for a more natural and less toxic cleaner to remove black mold, consider using white vinegar. The acid in white vinegar will kill black and green mold. The process for removing mold with vinegar is much the same as it is for chlorine bleach.
Begin by creating a solution of white vinegar that is three parts water and one part vinegar. Apply the solution using a mop, then scrub it vigorously with a scrub brush. You want the solution to penetrate the pores of the concrete, where it can attack the roots of the black mold.
For particularly difficult mold stains, let the solution soak into the concrete before scrubbing the area. Use a hose to remove the vinegar solution and the loose mold. If the mold remains, reapply the solution and repeat.
Once dry, spray on the bleach and water solution to prevent future mold growth.
3. Pressure WasherA pressure washer is one of the most effective means of removing mold from concrete. It’s especially ideal for treating large areas, such as a wall or an entire driveway, because it allows you to cover more ground in a much shorter amount of time than with a mop or scrub.
It also takes the elbow grease out of the process, replacing your arm with the power of high-pressure water to remove mold. Use a pressure washer with between 1,000 and 2,000 PSI. This creates enough force to clean concrete without causing damage.
When using a pressure washer, water alone isn’t good enough. You’ll need to use a mold and mildew concentrate in your pressure washer’s tank.
Pressure washers have different types of nozzles that exert different amounts of pressure on the house. Resist the temptation to use a high-pressure nozzle (typically red), as this can damage the concrete surface and isn’t intended for use with detergents.
Instead, use a low-pressure nozzle. Remove the mold by spraying the concrete surface, working from bottom to top if it’s a wall, while sweeping the pressure washer back and forth. This method prevents streaking on the surface.
Let the cleaner soak into the concrete for about 10 minutes, then switch to a higher pressure nozzle with a wide fan for rinsing. Use the same waving motion to rinse the cleaner and mold from the surface.
4. ZepIf you do plan to use a pressure washer to clean concrete, then you’ll need a concentrate. Zep concrete pressure wash is specially formulated for removing mold from concrete.
The nice thing about this product is that it functions as a great all-purpose cleaner. Not only will it take off your driveway’s mold problem, but it also includes a degreaser that will get rid of grease and grime. This makes it a great all-around option for driveways, walks, and patios.
Simply add 6 ounces of Zep to 1 gallon of water. For heavier stains, you can use up to 25 ounces per gallon. Apply using a cleaner applicator, allow to soak in for 10 minutes, then use a rinse nozzle to remove.
For tough mold stains, use a brush to scrub the product into the concrete after applying it. In addition to concrete, this product is also safe for asphalt, brick, and stone. Zep comes in 1-gallon bottles.
5. RMR-141RMR-141 is specially formulated to kill mold and mildew with two ammonia and chlorine-based active ingredients.
RMR-141 will kill 99.9 percent of bacteria and comes in a convenient spray bottle. This application method makes it ideal for addressing mold problems on concrete surfaces inside the home. It’s also certified by the EPA as safe for use indoors for mold remediation efforts.
It produces a low amount of harmful fumes, and, unlike other cleaners that have a harsh odor, RMR-141 leaves a citrus scent. These qualities make it an ideal option for treating indoor mold problems.
To use, simply spray RMR-141 on the concrete surface, allow to soak, and wipe clean with a cloth. Since RMR-141’s formula has a positive charge, it can better adhere to negatively charged bacteria and kill them. For extra cleaning power, use a chlorine solution when rinsing the solution off.
Because RMR-141 uses a small handheld sprayer for application, this product is best suited for smaller applications, such as a basement floor or wall or smaller spots on a patio or driveway. RMR-141 comes in 128-ounce bottles.
6. Simple GreenWhile pressure washer cleaners will kill mold, many also kill plants, shrubs, and even grass around a home. Simple Green formula won’t harm shrubbery or lawns. Because Simple Green’s products are non-toxic, this product is safe for use around children and pets and won’t harm the environment.
This makes it an excellent alternative to chlorine bleach, especially if you’re cleaning concrete areas close to landscaping.
Like other concrete cleaning solutions, Simple Green is an effective means of completing a comprehensive cleaning of a concrete patio, walk, or driveway. That’s because it includes a degreaser that kills mold and removes oil stains from any concrete surface.
To use, mix one part cleaner with 10 parts water. Dampen the concrete then apply using a pressure washer or manually using a brush or mop. For difficult mold stains, use a brush to scrub the product into the concrete.
Allow the cleaner to soak in for 10 minutes, then rinse using a hose or pressure washer. Simple Green comes in 1-gallon bottles.
7. Mold ArmorThis product makes outdoor mold cleaning easy by eliminating the need to mix solutions or pay for renting an expensive pressure washer. Simply hook Mold Armor up to a hose, and apply to a driveway, patio, or walk.
Mold Armor uses a chlorine-based solution that penetrates the concrete to kill mold at the root. For tough mold, use a scrubber to work the mold-free after applying the cleaner, then rinse with the sprayer. This product won’t harm grass or shrubbery, making it safe for use around landscaping.
In addition to cleaning concrete, Mold Armor is also effective at removing mold for siding, brick, wood, and stucco. Mold Armor comes in a pack of two 64-ounce bottles, which will clean up to 4,500 square feet.
How Do You Prevent Mold From Growing On Concrete?
The best way to solve a mold problem on concrete is to prevent it from happening in the first place. One way to do this is by eliminating the key element mold needs to grow, moisture.
For concrete patios, driveways, and walks, cut back foliage that creates shady areas on a driveway or walk that never see the sun.
Also, check for cracks in the pavement that can collect water and cause mold growth. Fill these cracks using a concrete repair product.
For areas where this isn’t possible, consider treating the concrete with an acrylic sealer designed for outdoor use. This prevents moisture from penetrating the driveway or walk, eliminating the environment mold needs to thrive.
For indoor areas, fix leaky pipes that are causing mold growth. For basements that flood, consider using a product such as Drylok to prevent moisture from entering the basement when it rains.
If that isn’t an option, a dehumidifier is also an excellent means of keeping the humidity level in a basement in check, preventing mold growth. Remove materials that can get wet and breed mold growth, such as cardboard, wood, cloth furnishing, and area rugs.
Also, check the areas around the foundation of the home. If the earth is not properly graded to cause water to flow away from the house when it rains, grading may be required. Keep leaves and other debris from piling up around the foundation, which can trap water and direct it through the foundation and into the basement.
Finally, make sure your home’s gutters properly direct water away from the home when it rains.
How to Get Rid Of Mold on Concrete Basement Walls and Floor
When mold is found in the interior of a home, it’s a much bigger deal because of the serious health hazards of black mold. For more extensive interior mold problems, it may be best to hire a professional mold mitigation service for removal.
If that’s not in the budget or you’ve discovered the problem while it’s still relatively small, you can do it yourself.
Begin by protecting yourself. Because mold can affect the respiratory system, it’s best to use a high-quality respirator to block out mold spores. Also, use rubber gloves and goggles for eye protection.
Create either a bleach solution or a solution of detergent and water. The Environmental Protection Agency suggests the latter as detergent can better penetrate concrete’s porous surface than bleach.
For thorough cleaning, use trisodium phosphate, an industrial-grade detergent that will kill mold and remove grease and grime. Apply the cleaner with a brush and scrub thoroughly to remove the mold and engage the roots. Wipe clean.
Once clean, use a bleach or vinegar solution and allow the solution to dry on the wall or floor. This will serve as a preventative to keep the mold from returning.
How to Remove Mold From Concrete Patio
Removing mold from an outdoor surface offers a broader range of options than mold removal for an indoor space. The best means for cleaning a concrete patio is a pressure washer with a PSI range of 100 to 200 PSI with a concentrated cleaner designed for mold removal.
A pressure washer will allow you to cover a large amount of space in a short amount of time.
Begin by adding the concentrate to the pressure washers tank and use a light pressure nozzle that won’t damage the concrete. Apply the cleaner to the patio in a sweeping motion, working from the house outward to avoid directing high-pressure water at the home’s foundation.
After applying the cleaner:
- Allow it to soak into the concrete for up to 10 minutes.
- Scrub any areas with significant mold growth.
- Don’t allow the cleaner to dry as it could stain the concrete.
- Use a rinsing nozzle on the pressure washer to rinse the cleaner.
If you don’t have a power washer, use a hose with a sprayer. You’ll need to apply a solution of vinegar or bleach and water and scrub with a brush before rinsing as the hose will not produce enough pressure to remove all of the molds on its own.
When dealing with black mold, it’s best to take the proper safety precautions to protect yourself.
Wear disposable gloves made from either latex, vinyl, or nitrile, making sure to choose the right size to prevent gaps that can allow made spores to get inside of them. Make sure to remove and dispose of the gloves when the work is done to prevent spreading the mold spores.Wear safety goggles to prevent mold spores from getting into your eyes. The goggles should fit such that there are no gaps around the eyes.
Wear an air-purifying respirator or face mask. N-95 masks filter out 95 percent of all particles, which is sufficient for mold removal, while an N-99 mask will remove 99 percent of all masks. A surgical mask does not offer enough protection as it is not designed for protection against mold spores.
While regular clothing that covers exposed skin is acceptable for smaller jobs, for larger mold removal, it’s a good idea to wear a Tyvek suit over your clothing. If you decide to wear regular clothing, make sure to remove and launder it as soon as you leave the worksite.
While it can be frustrating to find mold growth on your driveway, patio, or basement floor, there are simple methods for ridding your home of this unsightly and potentially dangerous invader.
Simple household cleaners such as laundry detergent and bleach are effective at eliminating both black and green mold. Commercial products also offer an excellent solution for mold removal.
Power washers can remove large amounts of mold quickly, making them ideal for outdoor use, while products that can remove the mold while releasing a low amount of fumes are ideal for indoor mold removal efforts.
Whichever method you choose, mold is potentially dangerous, so make sure to protect yourself when removing mold by taking the requisite safety precautions discussed above.