I found this in my pool area on the floor of my painted brick pilar.

Anyone know what it could be and the cause please??

Thank you :)

enter image description here

  • Bad pic? Changed your mind?
    – Huesmann
    Commented Mar 14, 2023 at 13:04
  • More details are required. Is it powdery or sticky. Are you able to wash it ? Commented Mar 14, 2023 at 13:39
  • A photo with context would help. I can't tell what I'm looking at.
    – isherwood
    Commented Mar 14, 2023 at 14:25

2 Answers 2


That looks like black mold, caused by water ingress.

Longer answer:

Theoretically it could be something else, but the root problem is the water ingress. Water in contact with masonry is always bad, that needs to be resolved.

  • It does look like it, but need it tested to be sure. No one can tell just by a picture or even looking at it. Can also be a leak picking up something black.
    – crip659
    Commented Mar 14, 2023 at 14:01

To be clinically correct it would have to be tested.

However here in Fla. that is everywhere outside where water is allowed to collect for more than a few days. We wash it away with a mixture of water and outdoor bleach. (so it doesn't harm any plants nearby) Sometimes a brush or broom is needed for a little scrubbing.

Clean it up and keep an eye on the area to see if the area dries, or continues to stay wet. if it stays wet you will need to find the source.

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