Getting Rid of Mold and Mildew on Concrete Surfaces: Effective Tips to Remove Mould and Mildew from Concrete

Concrete is incredibly durable and versatile, making it a standard choice for various surfaces, such as driveways, patios, basement floors, and garage floors.

However, a challenge arises when these concrete surfaces fall victim to persistent mould and mildew, damaging polished concrete‘s aesthetic appeal and structural integrity.

Mould and mildew, apart from causing unpleasant discolouration, can make the concrete slippery and potentially dangerous.

Plus, they can contribute to respiratory conditions and allergies, making it critical to keep these surfaces clean and well-maintained.

In this article, we outline a strategic approach to help Australian homeowners effectively remove mould and mildew off their concrete surfaces. We also provide guidance on how to maintain it.

Keeping Your Concrete Free of Mould and Mildew 

Here are 4 simple steps on how to remove mould and mildew from your concrete:

1. Prepare the area. Wear protective gear and sweep loose debris off the concrete surface.
2. Apply your chosen cleaning solution.
3. Rinse the surface thoroughly.
4. Dry the surface.  Make sure there is no remaining moisture in the concrete.

Here are some tips on how to keep mould and mildew out of your concrete surfaces:

1. Proper maintenance and regular cleaning are necessary to prevent the build-up of moisture and organic matter that can contribute to mould and mildew growth.
2. Mould and mildew thrive on moist, humid surfaces. Using a dehumidifier can help prevent mould and mildew by reducing moisture in the air.
3. Apply sealant to your concrete (two coatings if needed) is an excellent solution. Sealants can help prevent mould and mildew by creating a barrier that inhibits the growth of these microorganisms.
4. You can also use a power washer to remove mould and mildew from your concrete surfaces.
5. Regularly check your concrete for mould and mildew growth. If you notice mould growth early, you can take care of the problem right away before it has a chance to spread and do a lot of damage.

How Does Mildew and Mould Grow on Concrete?

Mould and mildew are common types of fungi that can be found in many environments, both indoors and outdoors. Understanding how mould and mildew grow will help you understand why they appear and how you can properly remove them from your concrete surfaces.

Mould

The first step in getting rid of mould is recognizing it. It might present itself as a stain, black spots or efflorescence on the surface of the concrete.

Mould thrives in damp, poorly ventilated areas, such as the basement or garage. A small area of mould can quickly spread spores, resulting in black mould on your concrete walls or floors. 

Mould needs moisture, warmth and a food source to grow. Here is where concrete becomes an easy target, especially if it’s unfinished concrete or external concrete surfaces, which are exposed to varying levels of humidity.

To clean mould from concrete, we need to disrupt this cycle.

Mildew

Mildew is a type of mould — a fungus that flourishes in damp conditions, often appearing on the top of moist surfaces.

In contrast to mould, which can have potentially harmful health effects and can penetrate the surface it grows on, mildew usually remains on the surface, where it can be easily removed.

However, if left untreated, it can cause unsightly discolouration and potential health problems.

Mildew usually manifests as a thin, powdery or fluffy layer, often grey or white, which can look like a light stain on your concrete surface.

This is particularly troublesome when it appears on exterior concrete, such as driveways or patios, where it can make surfaces slippery and hazardous, especially in rainy weather.

How to Remove Mould From Concrete

If you notice black or green stains on your driveway, patio, or garage floor, it’s most likely mould or mildew.

Here are simple steps on how to effectively remove mould and mildew from concrete.

1. Prepare the area

Before starting the mould removal process, you should prepare the area. Begin by wearing rubber gloves and ensuring proper ventilation to prevent inhaling the spores. Sweep loose debris off the surface with a brush or a soft broom.

If the area is indoors, open windows and use fans to improve air circulation. For outdoor areas, choose a cool, overcast day to prevent the cleaning agent from drying too quickly.

2. Apply your cleaning solution

Vinegar and bleach are both effective in removing mould and mildew from concrete surfaces. For a natural and safe option, mix one cup of white vinegar with one gallon of water.

Place the vinegar solution in a spray bottle and generously spray it onto the concrete, focusing on the areas with mould growth. Let it sit for a few hours before scrubbing it with a sponge or brush. Rinse with water and repeat the process if necessary.

You can also use a solution of one cup of bleach mixed with one gallon of water. Spray the bleach and water mixture onto the mould-affected areas and let it sit for about 15 minutes.

Scrub the concrete surface with a sponge or brush, then rinse thoroughly with water. Be cautious when working with bleach, and avoid using it on coloured concrete, as it may cause staining.

3. Consider a pressure washer

For larger areas or stubborn mould stains, using a pressure washer can be an effective solution. Before using a pressure washer, protect nearby plants and delicate surfaces with plastic sheeting.

Start by spraying the concrete surface with a mould-killing detergent or a mixture of water and bleach. Allow the cleaning solution to soak for several minutes, then use a pressure washer to wash away the mould.

Keep the nozzle of the pressure washer at least 12 inches away from the concrete to avoid damage. Rinse thoroughly with water afterwards.

4. Rinse with water

After letting the vinegar or bleach solution sit on the concrete for a few hours, it’s time to rinse the area. Use a hose or a bucket of clean water to thoroughly rinse the surface, ensuring all the mould and cleaning solutions are washed away.

Make sure to remove any residue and prevent any potential damage caused by leaving the cleaning agents on the concrete.

5. Let it dry

After rinsing the concrete surface, allow the area to dry completely. Keep in mind that drying times can vary depending on factors like humidity and temperature.

Make sure there is no remaining moisture from the concrete.

It’s best to wait until the concrete is completely dry before using the area again. This will ensure that the mould is fully removed and that the surface is ready for use.

Regular Cleaning and Dehumidifying

Regular cleaning of concrete surfaces can keep mould and mildew at bay. These fungi thrive in damp and humid environments, and concrete surfaces are susceptible to retaining moisture.

Surfaces like patios and driveways are at risk because they are exposed to the outdoors or areas with water contact. 

If you want a more comprehensive guide on how to clean concrete surfaces properly, you can check our article about the topic here.

Proper ventilation also aids in keeping the mould problem under control. You should increase the ventilation in your home, especially in damp areas, to improve indoor air quality.

Using a reliable dehumidifier can also prevent mould and mildew growth by reducing the moisture content in the air. A well-ventilated basement or garage restricts mould growth significantly.

Sealing Your Concrete

Sealing the concrete surface is a preventative measure, stopping mould from growing in the first place. Applying concrete sealers, especially a low-solids solvent-based sealer, can make the surface easier to clean and reduce the rate of mould growth. 

Sealants shut down pores and cracks in the concrete where mould may nestle and expand. Concrete walls in basements, patios, driveways, and exterior concrete can all benefit from adequate sealing.

Here’s a simple step-by-step instructions on how to seal your concrete:

1. Start by thoroughly cleaning the concrete surface. Remove any dirt, dust, or debris using a broom or a vacuum cleaner. If there are any stains or grease marks, you may need to use a concrete cleaner or degreaser and a scrub brush to remove them.
2. Allow the concrete surface to dry completely before proceeding. Depending on the weather and humidity, this may take a few hours or even a full day.
3. If there are any cracks or imperfections in the concrete, fill them in before sealing. Use a concrete crack filler or patching compound to repair any damaged areas, following the instructions on the product.
4. Apply a concrete sealer. There are different types of sealers available (e.g., penetrating sealer, acrylic sealer, epoxy sealer), so make sure to choose one that is suitable for your specific requirements. Read and follow the instructions on the sealer product carefully.
5. Pour the sealer into a paint tray or paint roller tray. Use a paint roller with a medium nap or a sprayer designed for sealing concrete surfaces to apply an even coat of sealer to the concrete surface.
6. Work in small sections, starting from one end and moving towards the other.
7. Make sure the sealer penetrates the concrete by back-rolling the surface with a clean roller immediately after application. This will help to remove any excess sealer and ensure a more uniform finish.
8. Allow the first coat to dry according to the manufacturer’s instructions. It typically takes a few hours, but it might depend on the type and brand of sealer you are using.
9. Apply a second coat of sealer following the same steps as before. This will provide extra protection and durability to the concrete surface.
10. Allow the second coat to dry completely before using the sealed concrete surface. The drying time can vary, so refer to the instructions on the sealer product for guidance.

Preventing Future Mould Growth

Mould regrows if not treated properly. Removal of visible mould might give you temporary relief, but it won’t guarantee that it won’t return.

Check areas that are out of sight — these are usually the ones causing the most damage. Also, be on the lookout for particular signs of new mould growth, such as musty odour or frequent allergic reactions.

Even if you can not see any mould growth, musty smells and water damage could hint at deeper mould problems.

Doing regular checks, keeping things clean, and quickly fixing any problems that could lead to moisture would likely ensure that mould wouldn’t have the chance to thrive.

How Stone Protection Can Help You Remove Mould and Mildew from Concrete Surfaces

If you’re unable to remove mould and mildew from your concrete surfaces despite repeated efforts, it might be time to rope in professionals.

Stone Protection can assess whether there’s a hidden problem causing the mould growth or if the mould infestation is so severe that extensive measures are required.

Remember, mould proliferation can lead to serious health issues and degrade air quality, so don’t let it sit on the concrete for too long. Contact us today!

Frequently Asked Questions

What do professionals use to clean concrete?

Professionals often use various methods to clean concrete, including pressure washing, chemical cleaners, and specialized equipment like floor scrubbers or polishers.

Is it safe to clean black mould yourself?

Cleaning black mould yourself can be safe if you take proper precautions, wear protective gear like gloves and masks, and ensure good ventilation. However, if the area is large or the mould is extensive, it is advisable to seek professional assistance.

What is the natural enemy of mould?

The natural enemy of mould is often considered to be sunlight (UV light), as it inhibits mould growth. Mold thrives in dark and damp environments, so exposing it to sunlight can help reduce its growth.

Can I use hydrogen peroxide for mould?

Mould can be removed with hydrogen peroxide, but it will not kill it. So, if you do not do something to stop it, it will almost certainly come back.