Prep first
Before you start
- Fix the water source first, or the mold will come back.
- Wear an N-95 respirator, gloves and goggles without vents so spores stay out of your lungs, off your skin and out of your eyes.
- Brush loose mold off outdoors if you can, so spores don't scatter through the house.
- Scrub the mold off with detergent and water, then let everything dry completely.
Mold on concrete is a living fungus that takes hold on a damp, porous surface, so it can sink in rather than sit neatly on top. Dry concrete soaks up cleaner along with the dirt it lifts, which is why the slab has to be wet before anything goes on, and most surface growth lifts with a wash. If there's a sealer or water repellent on the slab, cleaners can struggle to reach the growth, so test a small patch first.
Scrub with a stiff brush and rinse well, so the loosened growth doesn't dry back onto the slab. Black mold on a concrete floor or cement walls usually needs a mold remover made for masonry, not plain soap. Once it's dry, look at it in daylight, and call a pro if it still looks dark.
Before you start
What concrete, brick & driveways can take
Safe to use3
- Water
- Hot water
- Soaking
Use with care5
- Chlorine bleach
- Oxygen bleach
- Solvents (alcohol, spot removers)
- Acids (vinegar, lemon)
- Scrubbing and abrasives
6 items
What you'll need
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- N-95 respiratorKeeps spores out of your lungs while you scrub. (opens Amazon)
- Rubber glovesKeep the wash and the mold off your hands. (opens Amazon)
- Goggles without ventsProtect your eyes from splashes and spores. (opens Amazon)
- Mild liquid detergentThe only cleaner the main wash needs. (opens Amazon)
- Stiff non-metal brushScrubs the mold without leaving rusting particles behind. (opens Amazon)
- Bucket, sponge and clean clothsFor mixing the wash, scrubbing and wiping the surface dry. (opens Amazon)
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6 steps
Step by step
Step 1 of 6
Wet the concrete first
Soak the area with water before any cleaner touches it, and keep it damp while you work. Wet concrete keeps the cleaner from soaking in, so the wash stays on the mold where it can lift.
Step 2 of 6
Wash with mild detergent
Mix warm water with a mild liquid detergent until it's sudsy. Wipe the mold with a cloth or sponge dipped in the suds, covering the whole stained area.
Tip. Rinse the cloth often so you aren't spreading the mold around.
Careful. Keep the detergent wash out of your eyes, since it splashes easily when you scrub.
Step 3 of 6About 5 minutes
Soak the stubborn spots
Spots still dark after the first wash get the moistened detergent applied directly and left for about 5 minutes. Keep them damp while you wait so the cleaner keeps working on the growth.
Step 4 of 6
Scrub from the bottom up
Scrub with a sponge or a stiff non-metal brush, working from the bottom of each area up. Working upward keeps the dirty run-off from streaking the parts you've already cleaned.
Tip. Work in sections a few feet across, so each one gets a full scrub and rinse.
Step 5 of 6
Rinse well and wipe dry
Rinse the whole area with clear water until no suds are left. Then wipe the surface with a clean cloth so no detergent film is left behind.
Step 6 of 624 to 48 hours
Let the concrete dry completely
Leave the concrete open to air until it's fully dry. A wet area that dries within 24 to 48 hours usually won't grow mold again.
If you'd rather buy than mix
Best products for mold on concrete, brick & driveways
For a stubborn mark, test a hidden spot first, then repeat the detergent wash and rinse well before you try anything stronger.
Amazon Basics Microfiber Cleaning Cloths
How we picked these: each product is made for this type of stain, its maker doesn't warn against using it on concrete, brick & driveways, and its directions fit the steps above.
Finished the steps? How does it look?
Nice work. Let it dry completely and check it again in good light. Here is what done looks like:
How to tell it's really gone →A faint mark usually needs one more round, not a stronger product.
See what to do for what you're seeing →Heavy buildup usually takes more than one round.
Heavy or long-standing buildup →When to call a professional →How to tell it's working
Look at it again once the slab has fully dried, since a wet surface hides how much came out. If the patch still looks the same after a second full wash and dry, the growth has likely set into the pores, so turn to the set-in notes.
What changes for yours
Adjust for your concrete, brick & driveways
Concrete floors
Floors take the same wash, and the main difference is working in sections. Clean one patch a few feet across at a time, and rinse it before you move on so the rest of the floor stays wet and ready.
Joints and cracks hold dirty water, so use the brush to work into them and rinse them last. Watch for pooled water after rinsing, since standing water is the fastest route back to mold.
Concrete walls
Walls take the same wash, but water runs down them, so clean one section at a time and rinse it before moving up. Use a stable step stool or ladder so you can reach evenly without leaning, which keeps the scrubbing controlled.
Look above the stain for the water that caused it. A wall that stays damp from above will grow mold again no matter how well you clean it.
Mildew on concrete
Mildew is usually the lighter, surface-level growth, and the same detergent wash handles it. Stop after the wash and rinse if the surface looks clean, and save the stubborn-spot soak for areas that still look gray or dingy.
Don't assume the mildew is gone just because the color lightens. Let the concrete dry fully and look again in daylight, since damp concrete can look cleaner than it is.
Musty smell in concrete
A musty smell usually means growth or moisture is still in the concrete, even if the surface looks clean. Clean the area with the wash and rinse first, then track down where the damp is coming from before you decide the smell has gone.
Give the concrete time to dry through, then check the spot again with your nose and your hand. If the smell comes back once it's dry, the moisture source is still active, and that needs fixing before more cleaning.
Painted concrete or cement
Painted concrete takes the same wash, but paint lifts more easily, so scrub lightly. Clean and dry the surface completely before you paint or caulk over it, because paint over mold is likely to peel.
If the mold has grown under paint that's already lifting, scrape the loose paint before cleaning so the wash can reach the growth. Repaint only once the concrete has dried fully and no damp shows at the edges.
Black mold
Black mold is treated with the same wash, rinse and drying steps as any other mold, so you don't need a different product. What changes is how you judge the result, since dark staining can remain after the growth is gone.
If the dark color is still there after the wash and rinse, move to the stubborn-spot soak. Anything that stays after the poultice is most likely the stain itself, and it may not come out completely.
Green mold
Green growth on concrete responds to the same detergent wash, so there's nothing special to buy. Give it a careful scrub and rinse, and don't stop at a light wipe.
Once it's clean, dry the area completely and watch for regrowth in the same damp spots. If it keeps coming back, the water source still needs fixing before any further cleaning.
Heavy or long-standing buildup
Old mold that has been on concrete for months or years soaks deeper than a surface wash reaches, so the first pass may only lighten it. Repeat the detergent wash on the spots that stayed dark, then give them the five-minute soak before you rinse and dry.
If the stain has dried into a hard mark, a poultice does more than a wipe: spread a paste of talc, whiting, fuller's earth or diatomaceous earth, mixed with the detergent wash, at least 1/8 inch thick. Cover it with plastic for 24 hours, let it dry, then scrape or brush it off, repeating as needed.
If the stain is still there after the poultice, test a hidden spot with a commercial mildew stain remover before using it on the mark. Stronger methods carry more risk of damage to the concrete, so stop when the stain stops fading. Some older stains won't disappear completely, and that's the realistic result.
Vinegar, baking soda, peroxide and more
Do home remedies work on mold on concrete, brick & driveways?
Most home remedies come from fabric and kitchen cleaning, so only a few make sense on concrete. Concrete takes water, hot water and soaking well, so a few of these are worth a try.
Helps1Skip5
What makes it worse
Mistakes to avoid
Don't mix bleach with ammonia
Mixing the two gives off toxic gas, which is why the wash here uses detergent alone. Keep bleach and any ammonia-based product in separate jobs, and never use them in the same bucket or on the same spot.
Don't tackle a large patch alone
Mold covering more than about 10 square feet is more than a homeowner should handle alone, and so is mold that came from sewage or contaminated water. Follow standard remediation guidance or hire an experienced professional for either case.
Don't judge the spot while it's still wet
Wet concrete looks darker than it really is, so a patch that seems unchanged may already have lightened. Wait the full drying time, usually 24 to 48 hours, before you decide whether to scrub again.
Don't sandblast a moldy slab
Abrasive blasting permanently removes the surface, erodes the mortar, and lets water sink deeper, which makes regrowth more likely. A nylon or fiber brush with a mild detergent handles most surface growth without that damage.
Don't seal or paint over the mold
Paint over mold is likely to peel, and the growth underneath keeps going. Clean the slab and let it dry completely before any sealer or coating goes on.
Troubleshooting
If the stain is still there
Pick what you're seeing:
The mold keeps coming back
Moisture is still reaching the concrete. Fix the leak, seepage or drainage issue, and dry the area within 24 to 48 hours after any future wetting.
Streaks appear down a concrete wall
Wash from the bottom up and keep the surface wet until the final rinse so dirty runs can't dry in place.
A dark shadow remains after scrubbing
This may be cosmetic damage from the mold. Test a commercial mildew stain remover in an inconspicuous spot and follow its package directions.
Growth returns in the cracks and texture
Repeat the detergent dwell and sponge scrub on those spots, working the sponge into the texture, then rinse and dry thoroughly.
When to call a professional
Bring in a masonry restoration specialist if the slab is historic or part of an old structure, or if a sealer is blocking the cleaner. Stronger chemicals on a mark you can't identify can leave new stains that are harder to remove, so a testing lab is the safer route.
Questions
What kills mold on concrete?
A mild detergent wash removes most surface mold once the concrete is wet and the wash is rinsed off fully. For stubborn growth, a commercial mildew stain remover made for masonry is the next step, after a test on a hidden spot.
Are mold stains permanent on concrete?
Not always. Fresh growth usually lifts with the wash, but older growth can leave a shadow that's hard to lift completely. The set-in options lighten it as far as the concrete allows, and that's the realistic result.
Is black mold on concrete more dangerous?
Color alone doesn't tell you how risky mold is, so treat black and green growth with the same care. If the patch is bigger than you can comfortably handle, bring in a professional.
Why does mold keep coming back on concrete?
Mold returns when moisture keeps reaching the same spot, so the water source is the real problem and more scrubbing won't fix it. Look for leaks, runoff or damp spots near the stain, and fix them before you clean again.
Does mold on concrete mean the slab is damaged?
Usually not. Mold grows on the surface, and a clean, dry slab is typically fine once the growth is gone. If you see cracks or persistent damp spots, that's a sign to look deeper for the moisture source.
How do I know the mold is gone?
Once the concrete is clean and fully dry, the surface should look even, and any musty smell should be gone. If a dark mark stays after drying, that's usually the stain, and the set-in options are the next step.
Can I pressure wash mold off a patio?
Yes, but keep the pressure light. Stay at 400 psi or below, use a wide fan tip, and hold the wand at least 12 inches back, because high pressure erodes the surface and can make regrowth easier. A mild detergent with warm water usually does more than extra force.
Why do I need to wet concrete before cleaning it?
Dry concrete pulls the cleaner in and holds onto the dirt it loosens, so the mess can sink deeper than where you started. Wetting the slab first keeps the cleaner on the surface, where a clear rinse can carry it away.
Is bleach okay for mold on a concrete slab?
Bleach isn't the first choice for mold. EPA says it isn't recommended as a routine practice, so start with warm water and detergent. If you do use it, ventilate the area well and never mix it with ammonia, since together they make a toxic gas.
Mold on other materials
Other stains on concrete, brick & driveways
Start from the bigger picture
How we know this
Every method, amount and warning here comes from university extension services, industry bodies and product makers. We read them, check every step for unsafe combinations and changed amounts, and write it up so you can follow it.