Why Is My Patio Turning Black?

Stumbled upon this article because you saw your patio turning black?

Well, you must be glad to know you are not the only one. The black spots on your patio slabs could probably be:

  • Algae
  • Grease Stains
  • Black Lichen
  • Mold/Mildew

But do you know how it all starts? Or how to get rid of it?

This article discusses common causes of patios and how you can spot remover them without destroying your patio.

What Causes Patio To Turn Black?

Patio Black spots are those black spots that appear on the surface of most stonework after an average of two to three year period. There are multiple reasons why your patio might turn black or start growing black spots on it. They include:

1. Lichen

Lichens are the common reason you see black spots on your patio slab surface. It’s a composite organism that is developed from algae and fungi. They grow and spread on the surface of your patio. It thrives in the presence of moisture and shaded concrete surfaces like patio slabs.

Another reason you can see them growing on your slabs is that the wind quickly blows them onto your patio slabs. They can quickly establish themselves with their root-like structures and firm themselves onto the surface.

2. Water

Lichens are not the only reason your patio may turn black. It can simply be because of water. Water can quickly cause discoloration of your patio slabs, especially if there is a drainage issue or malfunction in the lawn irrigation system, making water spill onto your patio.

3. Three M’s – Mold, Mildew, and Moss

Do you know about the three M’s that nobody likes? Mold, Mildew, and Moss. Though nobody likes it, it is often found in places near you. These substances are quickly grown onto concrete surfaces with deep-level roots.

They can turn your patio slabs green or black.

4. Poor Workmanship

Another reason your patio slab is turning black can result from poor craft. If the slabs aren’t installed properly or cleaned properly afterward, they can be discolored due to poor material. Or the adhesive stains can turn darker when they haven’t been cleaned.

This is a rare cause to exist, but it does exist. Is this common?

Patios turning black are very common. It solely depends on how you maintain it and how you install it. As discussed above, there are multiple reasons for your patio to turn black and various reasons for your patio to get clean.

Several professional services provide this, or you can go DIY.

How to Prevent Black Spot on Your Patio?

Modern patio setup with rattan seating and a central fire bowl, well-maintained without patio turning black.

Avoiding black spots from your patio is the easiest way to eliminate them altogether. You can protect your patio using a patio sealer. Patio sealers perform multiple functions on your patios – they protect your patios against oil, dirt, and grease. They also seal the pores of your patios so that lichen doesn’t send tendrils into them in search of nutrients.

What To Do When My Patio Turns Black?

If your patio has turned black, multiple methods and products are available. However, ensuring that the method you adapt won’t harm nearby landscaping or the environment is vital.

Here are some of the effective ways to deal with patios.

1. Power Wash The Patio

The foremost thing you have to do to get rid of spots is to create a clean slab to work with. You have to power-wash the whole patio, remove the growing weeds and scrape off the Moss, algae, and fungus with a screwdriver with a flat head. Mostly, the power wash itself is enough to remove the black color of the patio, but if it doesn’t work out, then there are more steps to follow.

2. Pour Sand In The Patio Slab Joints

Another trick that works quickly is applying a thin layer of polymeric sand between the patio slab joints. Make sure to clean the sand from the top so it does not leave stains. Also, make it gets down right into the joints ultimately. The polymeric sand hinders weed growth and prevents the bugs and other insects from making their homes in between the stones.

3. Kill Weeds With Vinegar Solution

Strong chemicals can harm your surroundings, so your safe option is to opt for a vinegar solution. Use half a cup of vinegar and a half cup of borax, or add one teaspoon of vinegar to a spray bottle along with one teaspoon of dishwashing soap.

Spray it on the slabs as it will prevent the weeds from growing along with spreading Moss, mold, and mildew. So here’s the thing, it’s pervasive for patio slabs to get stained and black, but it’s not hard to get them back in shape.

So, the next time you see this happening, be considerate. Keep an eye on the cleanliness of your patio slabs. Dry out the slabs regularly and ensure a proper ventilation system.

This might mean trimming the overgrown shrubs and trees, placing the patio furniture in a different direction or place, or creating a proper drainage pathway to avoid moisture like pooling water.

Final Thoughts

Knowing what causes black spots will enable you to clear them quickly from your patio. However, cleaning your patio should depend on how often the black spots appear and how much mold, mildew, or Moss you have on the patio.

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