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How Do You Get Black Mold Off a Concrete Pool Deck?

Have you been noticing black spots on your concrete pool deck of late?  You might be wondering what they are. Chances are there is black mold growth on the deck. Black mold, or any mold for that matter, is unsightly, slippery when wet and can result in allergies. So how do you get black mold off a concrete pool deck?

You can get black mold off your concrete pool deck by spraying it with a mixture of baking soda, distilled white vinegar and water in a 1:5:5 ratio. Spray, wait for 30 minutes and then scrub clean with a stiff brush and soap water.

Be sure to protect yourself by wearing safety glasses, a mask and a pair of latex gloves. Also wear boots, a long sleeve shirt and trousers. Molds are spores that get airborne when dislodged. You do not want them entering your eyes, throat or lungs. If the spores land on your bare skin your skin may itch.

Depending on how severe is the growth of black mold and how deep are the roots, you may need to repeat the process more than once. Make sure to thoroughly clean the area with a garden hose or pressure washer after getting the black mold off the concrete pool deck.

Black Mold on Concrete Pool Deck

Can Black Mold Grow on Concrete?

Black mold can grow on concrete pool decks quite easily as the deck is often wet. Moreover, concrete is porous, so it retains water for much longer and remains moist.

Following areas of the deck will have a higher possibility of mold growth:

  • Areas under trees & other types of shade
  • Areas around potted plants kept on the deck
  • Areas with large cracks in the concrete

Mold spores, a kind of fungi, are in the air, everywhere, all the time. All they need is to find a spot on the concrete deck that can provide them with food, moisture & some shade. Mold thrives in such an environment.

Mold is green or black with a fuzzy or slimy texture. It may seem that the mold is only on the deck surface, but in fact it takes roots in the concrete cracks & pores. This is the reason that it is quite difficult to get it off.

They can even reappear, a few weeks after a thorough cleanup.

The adverse effects of mold on human health can include respiratory issues, such as asthma, heart problems, joint pain, migraines, fatigue and depression.

What Kills Black Mold on Concrete?

Mold, including black mold thrives when the environment is in neutral to slightly alkaline range. A pH level of 6.5 – 8.0 is most conducive to mold growth. 

In order to kill black mold on concrete you need to spray them with something acidic. Something with a pH of lower than 6.5. Of course you can not use something highly acidic as it will damage the concrete pool deck.

Some of the effective home made solutions are:

  1. A mixture of 1 part of baking soda, 5 parts of distilled vinegar and 5 parts of water
  2. A mixture of 1 cup of household bleach in a gallon of water
  3. A mixture of 1 cup of liquid chlorine in 2 gallons of water
  4. Undiluted white vinegar. No need to dilute it as it has only 4-7% acetic acid
  5. 3% Hydrogen Peroxide
  6. Juices of citric fruits such as lemons

You can also use some of the products that are commercially available. The advantage is that they are environmentally friendly and approved by the US EPA. And of course they are tried and tested so you can be pretty sure of the results.

Use a climate friendly, hydrogen peroxide based cleaning solution, such as Simple Green Oxy Solve. The product is safer for use around people, pets, wildlife and plants.

Check Out Simple Green Oxy Solve Total Outdoor Pressure Washer Cleaner

Simple Green Oxy Solve is pretty easy to apply. You can use hand cleaning or pressure washing, depending on your convenience.

Another great mold killer is WET & FORGET Moss, Mold, Mildew & Algae Stain Remover. Its outstanding features are:

  • Easy Spray & Leave Application
  • No Scrubbing, Rinsing or Pressure Washing
  • Bleach-free, Phosphate-free and Non-acidic
  • Surfaces Stay Clean 1+ Years in Most Cases
  • Safe for Virtually Any Outdoor Surface

Once the composite decking has been sprayed, just leave nature and time to do their bit. Most moss, mold, mildew & algae will start to disappear in a week or two. The more stubborn black mold may take a bit longer.

Check out Wet N Forget Moss Mold Mildew and Algae Stain Remover

How Do You Stop Mold from Growing on Concrete?

To stop black mold from growing on your concrete pool deck you must deprive the mold of three things they need to thrive

  • Food (including dust, rotting yard debris, etc.)
  • Moisture
  • Shade

As mentioned before, the area where you keep potted plants is quite susceptible to mold growth. You can, of course, still keep them but you must know How To Best Protect Pool Deck From Potted Plants

Concrete decks are porous and will hold moisture for a long time. This not only encourages mold growth but will also cause cracks in the concrete to grow with the freeze thaw cycle. 

It is extremely important to seal your concrete pool deck with a penetrating sealer. A penetrating sealer will seep into the tiny pores (capillaries) of the concrete, fill them up, solidify and block them, so that water can not enter. 

I recommend Foundation Armor SX5000 Water Based Silane Siloxane Penetrating Concrete Sealer.

The Armor SX5000 WB is a water-based Department of Transportation approved Silane-Siloxane penetrating concrete sealer. It penetrates deep into the substrate where it chemically reacts to form a hydrophobic barrier within the pores that reduces the absorption of water by up to 95%. Protects concrete, from within, without changing the look or feel of the surface. 

A topical sealer, in addition to the penetrating sealer, also helps seal cracks and other imperfections on the concrete surface.

Thank you very much for reading the post. I do hope you found it informative and helpful.

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