How to Get Rid of Mold on Concrete Block Walls – Step by Step Guide

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Your beautiful house won’t stay that way if you find mold on your concrete walls.

Mold does not only give an unpleasant look to your home but it is also hazardous to health.

For every homeowner, it is crucial to know how to get rid of mold on concrete block walls.

Read on for a guide to get rid of the unwanted mold from concrete – whether it’s in your kitchen, living room, or basement.

Get Rid of Mold on Concrete Block Walls

First, learn why mold happens. Knowing this will help you to prevent mold from happening again.

Mold can grow quickly in the presence of food and moisture.

You might think about how a concrete block wall can provide food. There’s a thin layer of dust that comes from the surrounding air, which is an excellent source of nutrients. In the case of moisture, mold occurs quickly as cement blocks easily absorb water.

The moisture barriers don’t always work. In the summer, mold grows faster because of the high humidity. A dehumidifier with a drain can keep the humidity at normal levels. It can still occur in the winter due to leaks.

Mold doesn’t require an ideal temperature to grow in your house. It only needs enough moisture and nutrients.

Read on for how you can get rid of the unwanted mold on the concrete walls of your house.

Method 1: How to Remove Mold from Concrete Block Walls

Pre-Step: Remove the source of the moisture

Before you start, you have to remove the cause of the mold first. That is the source of the moisture that is causing the mold.

If it’s a leaky pipe, fix the plumbing issue. If there was a flood, check that your sump pump is working and that the area is thoroughly dry with a fan. If there are cracks by the window sills or foundation that is causing leaks, some of them can be easily sealed with silicone caulk.

It can also be caused by high humidity that is above the level of 55%. That will cause dampness and condensation. You will need a dehumidifier with a continuous drain to fix this issue.

1. Gather Equipment and Prep for Safety

First, you want to gather your cleaning tools and safety equipment.

Mold can trigger asthma and other allergic reactions in people who are sensitive to mold. For those people, it is best to avoid this activity.

Safety Equipment
For safety equipment, you want to have gloves, a dust mask rated N95, and safety glasses.

If you’re dealing with lots of mold, you will also want a Tyvex suit to protect the mold spores from getting on your clothes.

What You’ll Need To Clean Mold

You have several options when it comes to what to use to sanitize the mold.

Hydrogen peroxide or OxiClean will work for generic cleanups. Scrub with a scrub brush.

If you want a deep clean, you can use what the professionals use. RMR-86 is a no-scrub formula.

For small moldy areas, use the RMR-86 spray bottle format.

For large moldy areas, you can use the 2.5 gallon size with a garden pump sprayer or professional spray bottle.

2. Vacuum the Excess Mold

You’ve got a big mold problem that needs the excess mold vacuumed first.

With a HEPA vacuum, choose the attachment and vacuum the excess mold. Only a HEPA-rated filter will be able to catch the small sized mold spores.

3. Spray down the moldy concrete

Next, with a cleaner of your choice, such as Oxiclean or RMR-86, spray down the moldy areas. Make sure it is generously wet.

In about 15 seconds, you can see the mold stains start to disappear.

If not, you can spray it again.

Some types of mold will require some light scrubbing.

4. Rinse with cloth and clean water

For indoor concrete blocks, use a cloth and clean water to rinse the clean from the concrete.

5. Dry

Let the surface dry by waiting 24 hours for it to dry completely.

You may use a fan or dehumidifier to help.

6. Optional: Run a HEPA Air Filter

To get rid of the mold spores present in the air of the room or basement, run a HEPA air filter for 4-7 days. That will get rid of the remaining mold spores suspended in the air.

Method 2: Steps to Remove Mold on Concrete Block Walls with Bleach

Step 1: Gather the required tools and materials

You will need a few essential tools and ingredients to get rid of black mold. You will need water, bleach, scrub brush, sponge, and a disposable towel.

Step 2: Take safety precautions

Mold is harmful to your health. You should be careful about breathing in the spores while working because it can affect your health.

Never use your bare hands to get rid of the mold. Before starting work, wear gloves, and protective clothing.

To protect your eyes, wear safety glasses.

If you have asthma, you should always wear a breathing mask rated N95 or a respirator before cleaning up mold.

Step 3: Identify mold

Mold and mineral deposits can look quite similar, and they can be hard to differentiate by observing.

Usually, mold will have dark areas and hairy looking substances. To be sure, take a spray bottle and fill it with water.

Then spray it on the areas. If the elements get mixed and dissolve, they are minerals.

But if nothing happens, it is black mold. Make note of those areas and go to the next step.

Step 4: Scrub the mold with a mixture of water and bleach

Now you will want to know, what kills mold? Will bleach help in killing mold? Bleach is the ultimate solution to remove mold. But only bleach might not be enough.

Take an amount of bleach and mix it with water. Then take a scrub brush and scrub the moldy area.

Make sure you’re wearing safety glasses to prevent any splashes from the scrubbing.

Dip the scrub brush in the mold and clean the concrete wall. After the mold is gone, you must rinse the area with clean water.

Step 5: Let the concrete dry

After you are done cleaning, let the surface dry by waiting 24 hours.

You may use a fan or dehumidifier to help.

Mold grows quickly in the presence of moisture. So it is crucial to keep the room and walls dry.

Otherwise, you will find mold growth again in a few days. If the concrete wall doesn’t get enough ventilation, use a dehumidifier. Or use a fan, and point it towards the wall.

Step 6: Prevent mold from growing again

It is not possible to clean the walls every day. To prevent mold from growing back, you can use a mold preventer spray.

Another option is to paint the surface with mold repellent paint.

They can help you prevent the regrowth of mold.

How to Get Rid of Mold on Concrete Block Walls

How Can I Remove Mold on Basement Wall Cinder Blocks?

The basement is the perfect place for mold growth because basements usually don’t have proper ventilation.

They quickly absorb moisture as they are typically made with cinder blocks.

All these factors make it easier for mold to grow efficiently on basement walls and floors. You might find different types of mold in your basement.

The important part is how to remove them. The process is similar to the previous methods with few modifications.

This process needs extra care because mold in basements are more intense, and they can reoccur quickly.

Step 1: Move everything before working

You must move things away from the area you will start cleaning.

Step 2: Clean the basement wall

Before applying bleach or detergent, you need to clean the basement walls.

Vacuum the excess mold with a shop HEPA vacuum.

Alternatively, use dish soap and mix it with water.

Pour the mixture into a spray bottle. With a sponge, wipe the walls to take off the excess dirt from the walls.

Step 3: Make the cleaner

You can use RMR-86 cleaner to get rid of the black mold on the wall. Or you can also use hydrogen peroxide.

If you’re using bleach, commercial bleach is toxic, so never use your bare hands to mix the solution. Take a bucket with warm water and mix a cup of bleach with it.

Step 4: Take a hard, bristle brush and scrub the basement walls

If there are several layers of mold, it can take more than one application.

You will need saturate the moldy area with the spray and then wait 10 minutes. Scrub and then reapply.

Then, wash the area with clean water and let the walls dry.


You can remove mold from concrete blocks with this step-by-step guide.

However, if you are dealing with a larger moldy area, such as over 10 x 10 feet of mold, it is best to let the mold remediation specialists do it.


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