
Concrete patios are prone to mould infestations, which can grow relentlessly and pose health and aesthetic concerns. Concrete is cool to the touch and can retain moisture, creating a habitable environment for mould. To prevent mould from growing on concrete patios, it is important to address the environment by improving ventilation, removing shade, and fixing grading and water drainage issues. To remove mould, there are several methods, including pressure washing, bleach, ammonia, vinegar, and laundry detergent solutions.
Characteristics | Values |
---|---|
Mold colour | Black, white, orange, green, purple |
Mold texture | Fuzzy or slimy |
Odour | Musty |
Location | Areas with prolonged dampness, water damage, or poor ventilation |
Removal methods | Pressure washing, bleach, ammonia, vinegar, detergent, scrubbing |
Protective equipment | Gloves, mask, safety goggles |
What You'll Learn
Pressure wash with detergent
If you want to avoid using bleach to clean your concrete patio, you can use a detergent designed for cleaning mould and mildew. This method is also effective if you're dealing with a large area, as it will make the task much easier.
First, make sure you have a detergent that is safe to use with your pressure washer. Fill the detergent tank and switch it on. Then, start spraying the concrete with the soap. Allow the detergent to soak into the mould and mildew.
Once the detergent has had time to soak in, start up your pressure washer. Using a powerful tip or turbo nozzle, hold the pressure washer about 10-12 inches from the concrete and begin blasting. The mould should break up and wash away quickly, leaving your concrete looking clean.
To avoid streaking, wash the patio in smooth, overlapping strokes to remove any other dirt or mildew. After cleaning, wait until the concrete dries to verify that you haven't missed any spots.
Safety Precautions
Before using a pressure washer, it is important to take some safety precautions. Make sure to wear protective gear, such as gloves and safety goggles, to avoid getting detergent or mould debris in your eyes or on your skin. Also, be cautious of water and mould debris spreading to other surfaces or entering nearby structures.
It is also recommended to pre-treat the affected area with a mild detergent or mould-killing solution before pressure washing. This will help to break down the mould and enhance the effectiveness of the cleaning process.
Cost Considerations
The cost of pressure washing with detergent can vary depending on whether you own or rent a pressure washer. If you need to rent one, the cost can be up to $50, and hiring a professional can cost between $80 and $350, depending on the size of the project.
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Bleach and scrub
Using bleach is an effective method for removing mold from concrete due to its strong antimicrobial properties. Before you begin, make sure to wear protective clothing, such as rubber gloves, safety goggles, and clothing you don't mind getting accidentally splashed with bleach. It is also recommended to protect any plants and landscaping nearby by watering them before and after applying the bleach solution.
To start, create a bleach solution by mixing one cup of bleach with one gallon of water. You can then apply this solution to the moldy concrete area. Allow the solution to sit for 10-15 minutes to penetrate and eliminate the mold. For mold and mildew stains, it is recommended to let the solution sit for up to 30 minutes to an hour.
Next, use a stiff brush or broom to scrub the area vigorously, dismantling and extracting the mold from the concrete. Make sure to scrub aggressively to get down into the pores of the concrete. Finally, rinse the concrete surface with clean water to remove the mold and any residue.
While bleach is an effective mold remover, it is important to note that it can be corrosive and potentially harmful to your health if used incorrectly. Bleach can also be harmful if inhaled, so it is crucial to work in a well-ventilated area. Additionally, never mix bleach with other household cleaning products, such as ammonia or vinegar, as this can produce toxic fumes.
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Ammonia solution
Ammonia is a highly potent and effective method for removing mold from concrete patios. Here is a step-by-step guide on how to use an ammonia solution to remove mold:
Prepare the Ammonia Solution
Dilute the ammonia with water, following a 1:1 ratio or the manufacturer's recommendations for dilution ratios. It is important to work in a well-ventilated area when handling ammonia, as the fumes can be harmful if inhaled in large amounts.
Apply the Ammonia Solution
Using a spray bottle or a mop, apply the ammonia solution directly to the moldy areas of your concrete patio. Ensure that you are wearing protective gear, such as gloves and a mask, to avoid inhaling mold particles or the ammonia solution.
Let the Solution Sit
Allow the ammonia solution to sit on the moldy surface for approximately 10-15 minutes. During this time, the ammonia will break down and penetrate the mold, making it easier to remove.
Scrub the Area
After the solution has had time to work, use a brush to scrub the affected area and remove the loosened mold. There is no need to scrub aggressively, as ammonia is effective at killing mold and forcing it to release from the surface.
Rinse Thoroughly
Once you have finished scrubbing, thoroughly rinse the area with a hose or power washer to wash away the ammonia and mold residues. Ensure that you rinse surrounding vegetation and surfaces to avoid any damage or harm to plants and pets.
Post-Cleaning Care
Even after rinsing, ammonia can be toxic to plants and pets if not thoroughly washed away. Be sure to properly ventilate the area and protect any surrounding vegetation and animals.
Using an ammonia solution is an effective way to remove mold from your concrete patio. However, it is important to prioritize safety and follow instructions on the packaging for safe usage.
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Vinegar solution
Vinegar is a great option if you're looking for a less harsh and more natural way to remove mould from your concrete patio. Used similarly to bleach, vinegar is known to kill many species of fungi, including harmful mould.
To make a vinegar solution, mix 1 cup of vinegar with 1 gallon of water in a spray bottle. If you need to treat a larger surface, you can double, triple, or quadruple this ratio and use a low-pressure sprayer. Spray the vinegar solution directly onto the mouldy area and wait for 30 minutes. After 30 minutes, spray the area again and scrub gently with a sponge. You should begin to see the mould and mildew scrub off. If there is still mould remaining, spray the area again with the vinegar/water mixture and wait another 30 minutes before scrubbing and wiping away the mould and mildew.
After removing the mould, you can use a penetrating concrete sealer to prevent it from growing back. By using a sealer like Siloxa-Tek 8500, mould, mildew, and organic growth will be reduced and easier to clean in the future.
It is important to note that vinegar can corrode coloured concrete finishes, so be sure to test it on a small area first. Additionally, vinegar is acidic and could eat away at the sealer or top cement layer of your concrete if left for too long.
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Seal concrete with a water-resistant coating
Sealing your concrete patio with a water-resistant coating is a great way to prevent mould from growing back. Concrete is porous, and when it comes into contact with water, it absorbs it. This can lead to structural damage such as cracks, frost damage, algae growth and salt corrosion. Waterproofing your concrete patio can prevent or significantly reduce this damage.
Types of Waterproofing Sealant
Firstly, you need to determine the amount of moisture present in the concrete. You can use a concrete moisture meter, calcium chloride test or relative humidity test to do this. If you find a high amount of moisture present in the concrete (over 3 lbs according to a calcium chloride test), it is best to use a moisture vapour barrier coating. If the moisture content of the concrete is less than 4%, you can use a penetrating concrete waterproofing sealer.
Preparing the Concrete
Before applying a water-resistant coating, the concrete must be free of all mould and mildew. You can use household bleach (one cup of bleach to 1 gallon of water) or vinegar (1 cup of vinegar with 2/3 cups of water) to remove mould and mildew from the concrete.
Choosing a Water-Resistant Coating
There are a lot of different options for water-resistant coatings, from chemistry to finish to features. For exterior applications like patios, Siloxa-Tek 8500 is a great option. It is a penetrating concrete sealer designed to treat a variety of applications with an emphasis on hydrophobicity and reduction of water uptake. It dries completely clear with a natural finish that will not change the look or appearance of the substrate. It is guaranteed to outperform all other concrete sealers on the market and is designed to prevent the growth of mould and mildew.
Applying the Coating
Always follow the manufacturer's instructions when applying a water-resistant coating. Make sure the concrete surface is clean and dry before applying the coating. Use a brush, roller or sprayer to apply the coating evenly to the surface. Allow the coating to dry completely before using the patio.
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Frequently asked questions
Dark or discoloured patches of black, green, brown, or white with a fuzzy or slimy texture are a clear indication of mould growth. Musty odours are also a sign of mould development.
Exposure to mould can be harmful to those who are allergic. Inhaling a lot of spores can also make you sick.
There are several methods to get mould off your concrete patio, including using a pressure washer, bleach, ammonia, vinegar, or laundry detergent.
First, put on protective equipment, including rubber gloves and a mask. Then, mix one cup of bleach with one gallon of water. Soak a brush in the solution and scrub the entire area until it's fully saturated. Let it soak for a few minutes before cleaning it up and rinsing the concrete surface with water.
To prevent mould growth, improve ventilation and drainage, and keep the area clean.