Nothing makes a homeowner’s stomach drop like spotting mold in, on, or near the house. It’s a pain to deal with: costly to remediate once it’s spread, painstaking to remove, and potentially detrimental to our health.
But is mold on the concrete patio really that big of a deal? After all, isn’t fungus a normal part of the outdoors, inevitable in some capacity? In short, the answer is that yes, mold on a concrete patio is a big deal, as it can cause lasting damage to surfaces and spread to your home.
Because it’s generally cool to the touch and can hang onto moisture, concrete can be a habitable environment for mold to spread, making mold in these areas essential to address at the first sign of trouble. So what should you do if you spot mold on your concrete?
There are several mold removal techniques you can employ that can nip your concrete’s mold growth in the bud before it has the chance to damage your patio or spread into the home.
Why Mold Grows On Concrete?
Concrete itself isn’t a food source for mold or other fungi. Unlike natural surfaces like trees, ground soil, grass, and other organic compounds, nothing about concrete’s makeup provides a source of nutrition that encourages mold growth. So, then, how can mold grow on concrete?
When searching for a habitable environment to reproduce, mold seeks out moisture, nutrition, and cool shade. So while your concrete itself doesn’t provide a nutrition for mold or mildew, if you have a portion of it that is consistently moist, dirty, and shaded, mold growth becomes likely. Put together the cool surface of concrete with sitting moisture or dirt, and you have a perfect environment for mold to thrive.
Is Mold on Concrete Patio Dangerous?
Not all mold is created equal: exposure to some types of mold can prove fatal, while other species are benign in human exposure. For instance, toxic black mold may be incredibly dangerous if it spreads to an inhabited area, but most other black-colored molds are relatively harmless.
But harmless or not, once mold finds a good place to propagate and begins to spread, it’s only a matter of time until it finds its way into the home, which is never a good thing. Here are some of the side effects of mold exposure to humans and dwellings:
- Staining: If left to propagate long-term, mold can cause staining to a concrete patio that can’t be reversed.
- Corrosion: Not only can mold cause discoloration, it can cause the concrete to corrode, ruining the smooth, flat texture it once had.
- Spreading: Mold grows. It procreates rapidly under the right conditions, and it can eventually spread into the home if not remediated.
- Health Concerns: Even on outdoor surfaces like a concrete patio, mold can prove harmful to those who are allergic.
How to Remove Mold From Concrete Patio: 6 Options
Unfortunately, cement mold removal is sometimes more involved than power-washing away all visible evidence of the fungus and calling it a day. Because individual spores are invisible and can begin to repopulate the entire area rapidly, it’s important to truly cleanse black mold off cement in its entirety or make sure it is killed at the root, so here are six full-proof ways to eliminate mold from any concrete surface.
1. Pressure Washer Mold Removal
For small, non-toxic infestations, using a power washer could be the easiest form of mold remediation. The pressure washer itself will easily remove any visible sign of mold, mildew, or other kinds of fungus. But keep in mind that unless a preventative measure is employed to prevent mold from growing again, it will be back as water alone does not kill mold. You must also make the area uninhabitable for fungus, but power washing is a good start for remediating mild concrete patio mold growth.
- Non-toxic, no chemicals needed
- By far the quickest, easiest form of mold removal
- Will not kill mold spores, only removes them
- Must be followed by mold prevention
The cost of time contributed to this form of remediation is minimal, and if you have a power washer the total cost of equipment is $0. But renting one can cost up to $50 and hiring a professional can cost between $80 and $350, depending on the size of the project.
2. Bleach and Power Wash
The first line of defense for many, thanks to its tried and true reputation, is to saturate the area with a bleach spray – composed of one cup of bleach and one gallon of water – followed by power washing. Concrete is hardy enough to withstand a power washer, and unfinished concrete isn’t susceptible to discoloration from bleach. Once the solution is applied and left to sit for one to three hours, killing the fungus from the source, a power washer is effective at removing all mold debris.
- Bleach is known to kill mold on contact, eliminating the problem from the source
- Affordable and relatively simple for the layman
- If the concrete is finished with a colored (or uncolored) seal, bleach may be corrosive
- Unless the source of the issue is addressed, bleach and power washing is a band aid solution
- Vulnerable people and pets should not be exposed to the fumes from a bleach solution, and it can be harmful if inhaled
Using bleach and a power washer is relatively cheap if you already own a power washer, in which case the only cost associated is the bleach itself, bringing the entire project to a total of about $10 or less. However, if you require the help of a professional it can cost anywhere between $100 and $400, depending on the size of your mold infestation. It is not recommended to remove the bleach solution by hand without a pressure washer, as doing so could result in skin burns and respiratory overexposure to chlorine bleach.
3. Vinegar Solution
While the bleach and power wash method is a go-to for many, a great deal of property owners would rather begin with a solution that’s less harsh and more natural. Vinegar is the perfect option in such cases. Used similarly to bleach, vinegar is known to kill many species of fungus including harmful mold. Spraying a vinegar solution (1 cup of vinegar per gallon of water) onto the surface, saturating it fully, should kill most strains of mold. Vinegar spray can be followed by power washing or manual hand scrubbing to remove the dead mold.
- Non-toxic and not harsh on skin or lungs
- Vinegar is available everywhere, and no power sprayer is required
- While vinegar kills many species of fungi, it isn’t a one size fits all solution, so research your mold variety to try to ensure vinegar is an effective chemical against your infestation
- Like bleach, vinegar can corrode colored concrete finishes
Thanks to the fact that vinegar can be washed off by hand, no power washer is required. If you have a small mold infestation, your cost of remediation could total around $3 for vinegar, $2 for a concrete scrubbing brush, and add in some elbow grease for a total of $5.
4. Mixing Laundry Detergent and Bleach
If bleach alone isn’t effective in remediating your concrete patio mold problem, consider adding laundry detergent into the mix. While bleach kills mold effectively, it is slick and non-penetrating and may not reach the root of a thick mold infestation. But laundry detergent acts as a trojan horse, ushering the bleach to the very core of your concrete pad mold infestation. Just add a cup of laundry detergent to your bleach and water solution, and allow it to sit on the concrete for a time, then wash the solution away with a pressure washer.
- More effective than bleach alone
- All ingredients are already readily available in most households and businesses
- Mixing chemicals can be dangerous, so this should be done outdoors and with plenty of ventilation
- Not recommended for use without a power washer, as heavy physical interaction with this mixture can result in skin burns and irritation to eyes and respiratory tracts.
Other than the cost of a power washer, this solution can range from $8 to $15, depending on the scope and product brands used.
5. Ammonia Mold Solution
Ammonia is probably the most effective chemical against mold. It kills on contact and it cuts to the source. While it’s incredibly toxic to breathe, ammonia is going to be your best bet against a fierce or widespread infestation, as it kills mold immediately and forces it to release from the surface. Ammonia solutions like RMR-141 are available expressly for mold removal, so follow instructions on the packaging for safe usage. The best part about ammonia is it requires neither scrubbing nor power washing, as it can cut through and kill thick layers of mold. You can simply wash it away with a regular hose once finished. You may elect to use a pressure washer or scrub away after, though, if you’d like the benefit of a visually spotless concrete patio surface.
- Ammonia-based mold cleaner requires no scrubbing to kill mold
- Ammonia-based cleaners can be scented and properly diluted for minimal respiratory discomfort
- Ammonia should not be used around children or pets, as immediate burns to the eyes and respiratory passages can ensue from exposure to non-diluted solution
- Kills mold on contact, but still requires use of a pressure washer or scrubber to remove mold debris
Ammonia solutions can range from $10 to $40 per gallon, depending on potency, brand name, and other added ingredients, and is usually diluted to around 1 cup per gallon of water. If you choose to use a scrubber or power washer to remove debris, that cost will be added as well.
6. Simple Green Solution
Simple Green is the best option for use on concrete patios near landscaping, sewn grass, or gardens. Because it’s all natural and safe for use near plants, pets, and children, Simple Green solution is a DIY mold removal favorite. While it doesn’t kill mold, the powerful degreasers in Simple Green force mold to release from the surface it’s infecting so it can be washed into the grass, mulch, or another organic surface. While use in a power washer is recommended, Simple Green can be sprayed onto the surface and washed away with a simple garden hose or wet sponge if needed.
- Simple Green is non-toxic and safe for use around pets, plants, and children
- Doesn’t require scrubbing or power washing
- Not as powerful at removing visible mold stains as bleach
- May require more than one application on thick mold
Simple Green solution costs around $10 per gallon, which should remediate a small to mid-sized patch of mold growth.
How to Prevent Mold On Concrete Patio
If you’ve developed mold on your concrete patio or sidewalk, chances are it will re-develop if preventative measures aren’t taken. If mold developed once, unless the environment is substantially altered to make it uninhabitable by fungi they will find their way into the area once more. But here are three ways to prevent mold on your sidewalk or concrete patio in the future:
- Remove shade: Since mold thrives in shady areas, trimming branches and removing other sources of shade can immediately deter fungi from growing.
- Increase ventilation: Mold can tend to develop in carports, garages, and on patios under decking structures because air doesn’t flow as freely in these areas. If the air feels stale and you’ve noticed some patches of mold, invest in an outdoor dehumidifier to prevent moisture from building up and leading to a mold infestation.
- Repair grading and water drainage: If you’ve noticed water standing or flowing where there’s mold, you could have grading issues on the premises. No matter how many times you clean mold in this situation, it will rapidly spread again each time water stands in the area.
- Keep it clean: While concrete is notoriously cool and damp, simply keeping it clean can prevent mold growth. If you don’t allow dirt or moisture to sit stagnantly for a long period of time, keeping the patio swept and hosed off, mold won’t have a foothold for growth.
What to Do If Mold Spreads Further?
If mold does spread beyond the scope of the original concrete infestation, becoming larger and more aggressive, you may need to use a combination of the above mold removal techniques and preventative measures, not only where the mold is visible but in the entire area.
However, if all else fails and your mold is peskier, more persistent, and more difficult to control than most, professional mold remediation is a good final step. Mold experts can test mold for its level of potential harm to humans and animals, remove and kill any mold present, and provide expert advice on next steps in preventing a future mold outbreak in and around the home.
How to Get Rid of Mold on Walls and Floor
Unfortunately, the nature of mold is that it spreads. If there’s mold on your concrete sidewalk or patio, there’s likely to be mold on your home’s basement walls or floor soon if there isn’t already. Here are some of the best ways to remove mold from concrete walls and floors, since the techniques on these areas vary slightly from exterior concrete pad mold removal:
- Strong vinegar solution: Similarly to removing mold from a concrete patio, do-it-yourself removal of mold from concrete floors and walls requires washing with a substance capable of killing the spores from the source. Vinegar is a child and pet friendly solution for interior walls and floors. Spray or wash it onto the walls or floors, let it sit, and scrub it off with an abrasive sponge.
- Chlorine bleach: If vinegar fails, using a chlorine bleach solution has a similar, but stronger, effect. Like vinegar, let it sit on the mold for a few hours before scrubbing away with an abrasive sponge. While this solution is neither pet nor child safe, and it’s recommended to wear protective gear when using, it is known to clean mold effectively. Pets and children may re-enter once the fumes dissipate.
- Ammonia and water: If all else fails, ammonia is one of the most capable solutions for removing bleach from hard surfaces. Use it in the same manner as vinegar or chlorine, but do not use near unprotected lifeforms like family members and pets. If you do choose to use this method, ensure your area is well ventilated and wear PPE.