Does Bleach Kill Mold on Concrete?

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mold on concrete, Does bleach kill mold on concrete patio stone floor

Mold is notorious for growing on any damp floor surface, like a concrete floor. Mold will make your driveway, patio, and steps look hideous and present health risk. The good news is you can use the most common household cleaning agents, to kill mold. But, does bleach kill mold on concrete?

Scrub and clean the mold-infested areas with a mold-killing household bleach/detergent and water. Scrub patiently to let bleach down into the pores and ensure mold is killed. Rinse to get rid of any solid organic matter out of the concrete.

Depending on your cleaning task, you might combine bleach with detergent. You can either use the mixture as concentrated or dilute it with water. Wear protective gear, you don’t bleach in your eyes, clothes, or even your skin. Ensure you have a well-ventilated area since the bleach fumes can be immense.

What Does Mold On Concrete Look Like?

On concrete, mold appears like spots of black, grey, or even greenish. The green mold, which is the most common type found on concrete, will stain and discolour your concrete, making it look old and dirty.

At times mold might look whitish though can be mostly confused with efflorescence, which also grows on concrete due to dampness. To distinguish the two, efflorescence easily dissolves in water.

Picture of mold on concrete floor, white mold on concrete floor

How to Use Bleach to Kill Mould on Concrete

First, you will need to wear protective gear and remember vigorous scrubbing will get the concrete clean, so you need energy for that too. Follow the steps below to get started on the cleaning process.

Items you will need:

  • Pail of water.
  • Mold killing liquid detergent.
  • Scrub brush or stiff-bristled sweeper.
  • Bleach.
  • Sponge.
How to get rid of Mold on Concrete & Patio Stone. Does bleach kill mold on concrete?

How to get rid of Mold on Concrete & Patio Stone.

Here are steps on how to prevent mold on concrete patio:

  1. Test a small spot to see if bleach or the detergent will discolor the concrete. Do not mix anything with bleach other than water. Some cleaning agents can produce toxic fumes when mixed with bleach.
  2. Mix one part bleach to three parts water in the bucket.
  3. Remove or cover any organic material that can be affected by the bleach solution.
  4. Use a dense sponge or scrub brush to apply the solution to the affected area on the concrete and clean vigorously. Do not use a wire-bristle brush as this will scratch the concrete.
  5. If the mold is not fading off, leave the solution to soak in for some minutes. Then scrub the area with the brush again until the mold is all gone.
  6. For effective rinsing, use hot water pressure as this will lift any organic matter that has seeped into the pores of the concrete. If you do not have water pressure, just use the regular water hose pipe. For the interior concrete, rinse and dry with a rag or towel.
  7. Clean and dry the items you have used and before setting them back to storage.

TIP: Cleaning only to kill mold will not stop it from growing back, instead address the source of the water causing the mold.

Is It Okay To Put Bleach On Concrete?

Concrete is prone to dirt, stains, molds, and mildew. Yes, you can make use of the bleach to clean the affected concreted area in your home. Bleach will not only remove the stains and dirt from the concrete, but it will also deodorize and kill the mold and mildew if used properly. However, there are a few things you need to know first about cleaning the concrete with bleach.

The type of bleach to be used also matters. Pure household bleach followed by an adequate hot water rinse causes no harm to your concrete. Use chlorine bleach to kill the mold spores and remove the stains effectively. Oxygen-based bleach will only remove the stains but not kill the spores.

Also, if your concrete is colored, the bleach might affect it. Fancy colored concrete should not be handled like the basic garage concrete floor. The harsh ammonia bleach endorsed for concrete cleaning will only ruin the color and sealant on this type of concrete. What’s more?

In case there are plants, furniture on the patio, or along with the steps, you need to remove or cover them as bleach will damage or discolor them.

Is Mold on Concrete Dangerous?

Regardless of where mold appears, it is a potential health risk, especially if you have the toxic mold. It weakens the concrete and even destroys the sealant. Those allergic to small stuff like spores may also react to the mold. Even those not sensitive to mold may experience fatigue, dizziness, and other complications related to mold. What’s worse is that once mold develops on concrete, it starts spreading to sinks, tiles, wood, and other parts of the house.

Can Mold grow on Concrete?

How to Remove Mold from the Concrete Patio?

How-To Clean Mold from Concrete | | 800-997-3873

The paramount solution is to scrub and clean the troubled areas on the patio with a simple solution of household bleach and water. Be sure to wash aggressively to get down into the pores of the concrete. Let the detergent or bleach solution soak in for a while to ensure that the entire mold is killed. For densely stained patios, use a pressure water pipe to clear off the whole mold.

How to Get Rid Of Mold on Concrete Block Walls?

Basement Mold Removal - How To Remove Mold

Clean your cinder block wall regularly with a solution of water and bleach or mild detergent. Mix one part bleach with three parts of water in a pail. Using a scrub brush or sturdy sponge, briskly scrub the affected wall with the bleach/water solution until the mold spots have vanished.

Mold-Killing Detergent for Concrete

Best products to remove outdoor mold, mildew

Mold-killing detergents for cleaning concrete are not as powerful as using other home remedies like bleach, vinegar, and baking soda. In most cases, you can use them alongside these other mold removal solutions. However, find out which if it is safe to mix with any of the other solutions to avoid producing toxic gases.

How to Clean Mold off A Concrete Floor

How Do I Clean Mildew on Concrete Floors? : Bathroom Cleaning & More

First, moisten the concrete floor with water before cleaning off the mold. Eliminating mold from a little damp floor will lessen the number of mold spores released into the air during removal. Use the correct amount of bleach, vinegar, or mold removal detergent and scrub the mold off entirely until it disappears. Finally, rinse the area clean and leave it to dry.


While using the available home remedies for cleaning mold, be cautious about the various effects each has on the concrete floor. Be careful also not to mix what is not recommended for your safety. Mold removal should be dealt with from the source of the problem rather than the surface. After cleaning, look for the source of the mold to avoid future breakouts. You may also apply a penetrating sealer to prevent mold and mildew growth on your concrete floor.

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Joe McGuinty
I’ve been working with floors for over 12 years. I started as a flooring contractor, primarily in materials selection. Then, I switched careers into accounting, so my wife and I began buying, renovating, and re-selling homes on the side. You’d be surprised how much value you can add to a home simply by adding new floors.

1 thought on “Does Bleach Kill Mold on Concrete?”

  1. A wet concrete bathroom floor can be a long and tedious process to determine the source. I have one that I thought was groundwater wicking through. No rain for several months said otherwise. I thought it could be a water pipe leak. Turned off the main for several weeks and it had no effect. No water supply and no rain and it still gets soaking wet ???? The only possibilty left I can think of is a galvanized pipe from the well is transitioned to cpvc at one far corner of the house and the connection or the galvanized pipe is leaking underground. I guess it’s time to break out the shovel.


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