How to Get Rid of Mold on Concrete Block Walls

Mold on concrete walls can be a real problem, especially in basement locations. Mold needs warm, moist places to grow.

Concrete blocks gets very hot in the summer and stays fairly wet from either condensation or ground water most of the year. 

Why Concrete Blocks are Susceptible to Mold

The thermal mass of concrete blocks and the rough texture make them a perfect place for mold to grow.

Also, concrete block is much cheaper than brick or stone so it is typically used around places like barns.

Unlike around your home, these areas aren’t maintained so there are cracks and crevices in which water can collect that provide an ideal environment for mold to grow.

The Mold-Fighting Solution

Since mold can be both a health risk and an eyesore, many homeowners want to remove it from their walls. Unfortunately, most solutions online are ineffective for concrete blocks.

The following tips will help you effectively clean your wall of mold while keeping within OSHA safety standards so that you don’t harm yourself or others. 

Safety First

Important Note: Always Wear Rubber Gloves, Eye Protection, and ensure the area is well ventilated. 

Before doing any mold cleanup, you should be mindful and if have severe allergies, weak immune system, or have other health problems, consult your doctor before attempting to do mold removal.

Even small areas can pose a risk. The recommendations discussed apply to mold caused by clean water and areas that are less that 10 square feet. 

Mold growth over 10 square feet or caused by sewer backups or unsanitary water should be handled by a professional remediation contractor.

Wear Your Safety Gear

Wear rubber gloves, respiratory protection, and safety goggles when you have to deal with mold because it causes skin irritations and allergies that aren’t fun to deal with.

If you’re allergic to mold then respirators may also be required so make sure before entering the area that you are well equipped to deal with any potential problems that may arise.

Mold Cleanup Steps to Get Rid of Mold on Concrete Block Walls

These steps can be used after the moisture source has been found and fixed.

Step 1) Cut off the power in the area you’re working in so that sparks are not generated by your vacuum or other tools during cleanup.

When using a wet vac, get enough distance between it and the mold so that any static electricity discharge won’t be strong enough to ignite some combustibles.  

Step 2) Grab a trusty HEPA vacuum which should be used even when cleaning up drywall dust because you never know what’s on those bricks.

The only exception would be if all surfaces are clean of spore-laden dust then a regular vacuum is good enough.

Step 3) Make sure your vacuum hose isn’t too long so that it will drag and stir up mold spores while you’re cleaning. A 6 ft. hose should be more than adequate for this job so adjust the length to about half of that if possible. 

Step 4) HEPA vacuum any surface growth as well as deep down in corners with round attachments or crevice tools.

Don’t use abrasive discs because they can cause damage to the concrete block and you have nowhere else to go after scraping! 

Step 5) Use a detergent solution to clean the easily accessible surfaces. Use a scrub brush or wire brush to get rid of any mold that has grown deeply into the pores. 

Step 6) You don’t have to but you can apply a biocide such as Benefict Decon 30 – plant based cleaner to the treated areas on your walls wherever there are visible signs of mold growth.

This will kill off any mold spores it comes in contact with which should prevent any future growths in those spots while working its way inside existing colonies for complete eradication.

Step 7) Make sure you wash your hands thoroughly when you’re finished to ensure that none of the mold gets on your skin or is inhaled while you’re working.

If you feel any type of rash or irritation occurring during cleanup, then stop using the solution and seek medical attention.

Step 8) Let everything dry for at least 24 hours before applying any sealants or water proof coating. Once the area is dry, go ahead and replace any panels that were removed earlier in this process or you can use a concrete sealer to paint the entire wall if necessary. 

Quick tip, after all the mold has been removed from the wall and the area has been sanitized, you can use a air scrubber to circulate the air to speed up the drying process.

Step 9) Make sure that if your concrete blocks have already been affected by natural minerals leaching through them that they are sealed again with a penetrating sealant so that it can’t happen in the future. 

Step 10) If you want to ensure you never have this issue again look into dehumidifiers because moisture is the only way mold can grow on concrete block walls so running fans can help circulate air but won’t actually remove the water source to prevent future growths. 

Preventing Mold Regrowth on Concrete Walls

So now you have successfully removed the mold from your concrete walls.

You’ve done the hard work, now it’s time to prevent it from re-growing. Here are some quick tips of what you can do to prevent mold growing on concrete walls in your home.

Mold Prevention Tips:

1. Allow the surface temperature to drop 10 degrees before you paint or apply a non-porous coating.  Always follow the manufacturer’s application instructions when applying sealants to the walls in your home.

2. Keep your household and areas in basements humidity below 50% with a dehumidifier if needed in extreme cases.

3. Ventilate your shower after every use to avoid moisture build-up on walls /shower liner/set (if applicable). Mold can grow within 24 hours. 

4. Allow your concrete walls to dry out naturally, do not use a towel or blow dryer to speed up the process.  

If you are concerned about the mold growing on your wall, a nonporous concrete sealant from various brands of paints can be applied to prevent growth and eliminate any mold that has already started to grow. 

Nonporous Coating Tips

1. For smooth concrete walls, use a roller or spray apply a sealant that can be found at any hardware store.

2. If you have grooved concrete block walls, us a sprayer to apply sealant to these areas quickly and easily.

Things to Avoid

1. Do not paint or apply a non-porous coating when the surface are too cold or wet.

2. Do not use any type of brush on concrete block walls. Nonporous coating will not adhere correctly to the grooved surfaces of concrete block walls with a brush, so it is best to use a spray application instead.

Four other tips on how to successfully remove small mold Grove sites from your home please review the other blogs on our site that may be of use.



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