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How To Remove Mold From Concrete Basement Walls In 4 Easy Steps

There are few settings more ripe for mold growth than a basement. Dark, damp and humid, basements provide the ideal conditions for mold to grow. Concrete walls become mildewed when spores grow on dust, dirt, or painted surfaces. Thankfully, basement mold removal doesn’t have to be a struggle, and you can do it yourself with basic supplies and a little patience. You can effectively kill mold with a lot of household supplies like vinegar along with other cleaning solutions commonly found in stores to get rid of any mold stains. 

mold on concrete basement walls

Why Mold Grows in Basement Walls

Mold of any kind like black mold can grow anywhere there is moisture, oxygen, and organic material. It’s especially happy in damp and humid places, but even the slightest bit of moisture can jumpstart growth. 

Moisture gets into basements and crawl spaces for a variety of reasons. For one, there’s the location: as they are carved directly into the ground, basements require extra care to seal off groundwater and other moisture sources. Plumbing and HVAC systems often run through basements, and condensation and leaks can be a real issue. Plus, basements commonly have high humidity levels.

Many people also keep washing machines, freezers, and other potentially leaky appliances in the basement. With little air circulation and nowhere for evaporated water to go, it’s an ideal home for spores to flourish. Poor drainage in a backyard or near a basement door can also cause flooding. When flooding occurs and your sump pump stops working, this can also have severe consequences. A sump pump failure will lead to an excessive moisture problem and then lead to mold in your basement and even exterior walls. 

The best way to prevent growth is to keep things as dry as possible. Make routine checks for wet spots. At the first sign of moisture intrusion, add a dehumidifier to the basement. This can help keep mold spores at bay until you eliminate the source of excess moisture. If your basement is prone to flooding, you may want to invest in basement waterproofing efforts or improvements to your gutters and drainage systems.

Supplies & Tools: A high-quality bristle brush or scrub brush is the key to cleaning mold from basement walls, concrete blocks and other surfaces. Choose one that features stiff fiber bristles instead of a wire brush. You’ll want something tough enough to withstand some serious elbow grease without damaging your walls. For drywall, skip the brush and opt for some gentle sponges, so you don’t damage the wall surface.

Speaking of scrubbing, get a strong enough cleaner to remove mold that’s gentle enough not to compromise your walls’ structural integrity. The U.S. Environmental Protection Agency recommends using detergent and water, but there are other options as well.

For concrete basements, start with hydrogen peroxide. It’s a fungicide, and bactericide that will kill off any living organisms clinging to your walls. A simple household chlorine bleach solution and water can do wonders. Vinegar’s acidic nature is an excellent solution for attacking those surfaces and often used to kill mold. Don’t worry about the smell: once it’s dry, the odor will dissipate.

Mold exposure can cause allergic reactions in some people, so as you clean, make sure to wear the proper safety gear and safety equipment. Invest in a pair of rubber gloves, safety glasses for eye protection, and an N95 face mask to minimize exposure as you scrub.

4 Steps To Remove Mold From Concrete Basement Walls

removing mold from concrete walls

Step 1: Improve Ventilation 

If mold growth has already begun covering your walls, taking swift action is critical. But before you start scrubbing, make sure the basement is as well ventilated as possible and turn on any fans. Proper ventilation helps dry things faster and also helps remove chemical odors, plus also significantly reduces the chance of household mold issues and prevents future mold growth. Poor ventilation is a leading cause for mold infestations. 

Step 2: Spray Basement Walls With Cleaning Solution

Pour your solution of choice into a spray bottle. To remove mold from basement, heavily spritz the surface with the solution. Be sure to let the solution soak in for a while before scrubbing to help get rid of mold – you’ll want to ensure all spores are killed off before taking a bristle brush to the concrete wall. After waiting for about 30 minutes, scrub vigorously (but be gentle enough not to cause damage to walls) with the scrub brush. 

Step 3: Rinse The Concrete Walls

If possible and practical, rinse the solution off the walls using a water hose. Some household owners have even looked into using high-pressure washers to help remove mildew and get rid of mold from basement walls. Warm water from your sink will also do the trick. Rinsing helps remove any lingering spores that are clinging onto the wall.

Dry the rinsed surfaces with a towel to minimize the risk of further mold spores. You can also use a negative air pressure machine to filter the dirty air in your basement. 

Step 4: Use Borax To Prevent Mold Regrowth

If you’re hoping to prevent mold from returning to your basement, you may also want to pick up some Borax. Borax repels mold, and a thin layer applied after cleaning can ensure your walls aren’t harboring any lingering spore growth. 

With regards to mistakes to avoid, sometimes people opt to paint over their concrete basement walls after removing mold. Painting over mold won’t kill any lingering spores or get rid of mold spots on the walls. Instead, spores become trapped under the layer of paint and will continue to be released – even if you can’t see the growth through the paint. 

Mold remediation takes time. While the actual removal may only require a bit of hardwork and relatively little time, you’ll want to monitor your walls for a few weeks after cleaning. Spores are invisible to the naked eye. So, while you might have thought you did a thorough job in the removal process, you never know what might be lingering. (Don't forget to invest in an air scrubber to filter the air after). Keep an eye out for mold on concrete before you decide to paint. Otherwise, follow the steps above to clean mold effectively. 

If in doubt, call on the Pros. It’s easy to get in over your head when it comes to mold removal. When in doubt, turn to the professionals for guidance.

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Caleb Davis

Caleb Davis is a Water Restoration Lead Technician with Roto-Rooter Salt Lake City. If you need help with water damage or removing mold from your walls, give Caleb and his team a call.