If you are reading this, I’m assuming you have black spots (black lichen) on your patio slabs that you want to get rid of?

I have the perfect solution for you that is quick and easy – without damaging your patio slabs!

To get rid of black spots on your patio you will need to use some form of chemical like Patio Magic, Wet and Forget, or Pro-Kleen Black Spot Remover. Unfortunately, no matter how powerful your pressure washer is, it won’t remove the black spots.

In this article, I’m going to show you how to use various chemicals to get rid of black spots on your patio slabs which will be both quick and easy.

If you are looking to maintain your patio this year, you might find this article handy – When Is The Best Time Of Year To Pressure Wash Your Patio And Driveway?

What Are The Black Spots On Concrete? (What causes it)

The black spots that you see on your patio (also known as Lichen) is an organism that thrives in damp conditions. A lichen, or lichenized fungus, is actually two organisms functioning as a single, stable unit. Lichens comprise a fungus living in a symbiotic relationship with an alga or cyanobacterium (or both in some instances). There are about 17,000 species of lichen worldwide.

Don’t worry though, the lichen that lives on your patio slabs is not harmful to humans, but it does leave a black stain on the surface of your patio.

Note: The more concrete you have in your patio slabs, the less likely you are to get black spots. The more natural the stone, the more likely you are to get black spots.

What Are The White Spots On Paving Slabs?

Efflorescence is a white or grayish salt deposit that forms on the surface of brick, concrete, stone, stucco, or other building materials when water is available. It has a whitish or grayish tone and contains salt deposits that remain on the surface after the water evaporates.

Oftentimes, you see them on your brickwork, paving slabs, and patio slabs.

Efflorescence is not harmful to humans, but it can be a nuisance because it makes the surface of the building material look dirty. It can also be an indicator that there is water present in the masonry, which can lead to problems like spalling, efflorescence, and freeze-thaw damage.

Related: What Is The Best Paving For Patios?

How To Remove Black Spots From Paving Slabs

There are various different ways of removing black spots from your paving. You can either purchase store-bought chemicals or produce your own from household ingredients.

In this section, I’m going to show both methods. Whichever one you choose to use will be effective, it all depends on your budget and how much time you want to spend on the project by producing your own formula.

Do these black spot removers work?

Yes, these black spot removers do work. As long as you follow the instructions on the bottle, it will remove the black spots from your paving slabs.

Related: Do Slate Patio Slabs Scratch? (A Quick No-nonsense Guide)

Store-Bought Black Spot Remover

Here is a list of store-bought black spot removers that you can use:

Jeyes fluid black spot patio

Jeyes Fluid is a great, multi-purpose exterior cleaning solution. If you have a patio that has an unsightly black spot/lichen on it.

Patio magic

Patio Magic is ideal for killing and controlling most algae, moss, and mold on driveways and patios in a single application.

Related: How to Remove Green Algae from a Wood Deck (TODAY)

Wet and forget

Wet and Forget is a moss and algae killer that will remove the black spots from your paving slabs with just one application.

How does wet and forget work?

Wet and Forget works when you spray it onto the surface of the paving. The Wet and Forget formula will attach itself to the moss or algae and start working immediately. The Wet and Forget formula will then start to break down the cell walls of the moss or algae, which will kill it.

Pro-kleen black spot remover

Pro-Kleen Black Spot Remover is a powerful degreaser and cleaner that can be used to clean a variety of surfaces, including concrete, brick, stone, and stucco.

Universeal No More Black Spot Remover

No More Black Spot is a professional-grade outdoor cleaner that says it eradicates all signs of obstinate grey/white lichen and common black spots.

If you live in the UK, you can also purchase store-bought black spot removers from B&Q, Screwfix, and Homebase.

The downside to using store-bought black spot removers is that they can be expensive, and sometimes they don’t work as well as they promise.

All of these products work in a similar way – by dissolving the lichen on your patio slabs.

Producing Your Own Homemade Black Spot Remover Formula

If you want to produce your own black spot remover formula then it will need to have Sodium Hypochlorite (commonly known in a dilute solution as bleach). This is the main active ingredient that will dissolve the lichen.

Other ingredients that you will need are:

  • Water
  • White vinegar
  • Salt

Here is a recipe for a homemade black spot remover:

1 liter of warm water

1 cup of white vinegar

1 tablespoon of salt

Related: Household Goods That Make Excellent Diy Cleaners

Method 1:

1. Add the warm water, white vinegar, and salt to a clean spray bottle. Shake well to combine.

2. Spray the mixture onto the black spots on your paving slabs.

3. Leave for about 15 minutes to allow the mixture to work its magic.

4. Rinse off with cold water and dry with a cloth.

The great thing about this method is that you can make as much or as little as you need, and it’s a lot cheaper than buying a store-bought black spot remover.

Whichever method you choose to use, it will be effective in removing the black spots from your paving slabs. Just be sure to follow the instructions on the bottle or recipe to

Note: Ensure you take the correct precautions when mixing chemicals like bleach, such as wearing plastic goggles and protective gloves.

Method 2:

Here is another recipe that you can use:


1 part bleach

4 parts water


1. Combine the bleach and water in a container and stir well.

2. Pour the mixture into a spray bottle and spray it directly onto the black spots on your paving slabs.

3. Leave it to soak for 10-15 minutes before rinsing off with water.

4. Repeat as necessary until all of the black spots have been removed.

The downside to this method is that you need to make a fresh batch every time you want to use it, and it can be dangerous if not used correctly.


Does Bleach Remove Black Spots On Patio?

Yes, bleach does remove black spots from your patio. Before they reveal on the surface, black spots send tendrils into the paws of your paving slabs, so be sure to treat all of your paving slabs, even if they appear clean. Wet the surface of your patio before using the diluted bleach and make sure to avoid over-spraying onto the plants and grass around it.

Related: 5 Ways To Clean A Concrete Patio Without Killing Your Grass

How To Remove Black Algae From Concrete

To remove algae from concrete you need to:

Sweep the concrete with a broom to remove any loose dust and dirt.

Mix 1 cup of ammonia and 1/2 gallon of warm water in a bucket.

Apply the mixture to the black stain and let it stand for 5 minutes.

Wet an old towel or shop towel with warm water from a sink.

What causes black spots on patio slabs?

Black spots on your patio slabs are the result of black lichen. The spores from the black lichen begin as tiny dust-like spores that develop on the undersides of leaves on trees and shrubs. In their millions, these spores are carried by the wind and rain to your stonework.

How to clean concrete patio without killing grass

To clean a concrete patio without killing grass means you need to use a chemical that does not contain any harmful chemicals like bleach. Chlorine bleach is a popular and effective choice for cleaning concrete, but it will kill any plants or grass it comes into contact with. For this reason, you should avoid using chlorine bleach if you want to clean your patio without harming the grass.

There are several other types of bleaches on the market that will not harm plants and grass.

You can use ordinary household dish soap, A 3-tablespoon dish soap solution mixed with 1 gallon of water can be used to clean the porch without damaging surrounding plants. When shopping for liquid dish soap, look for one that doesn’t contain additional chemicals such as bleach or fragrances.

Related: How To Clean A Patio (Without Chemicals)


Removing black spots from your patio slabs isn’t really that hard. As long as you follow the instructions for the method you choose, you’ll be able to get rid of those pesky black spots in no time!

What have you used to remove black spots from your patio slabs in the past?

Let us know in the comments below.

Some other useful articles:

Does Bleach Remove Black Spots On My Patio?

The Cheapest Way to Lay a Patio (INC. THE BEST MATERIALS)

How To Remove Moss From Patio And Driveway Block Paving 

Patio Laying Guide (In Just a Weekend)

The Patio Guide: (Everything You Needed to Know)

About the Author

Passionate about helping households transition to sustainable energy with helpful information and resources.

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