Green or black growth on a patio, pool deck, sidewalk, or north-facing driveway is usually algae. Besides looking bad, it makes concrete slippery when wet. Here is how to remove it.
The Short Answer
To remove algae from concrete, apply a cleaner made to kill algae, let it work for a few minutes, then wash the surface with a pressure washer and a surface cleaner and rinse. Pressure alone often leaves the roots behind, so the growth returns quickly.
Why Algae Grows on Concrete
Concrete is porous and holds moisture. Shade, sprinkler overspray, poor drainage, and nearby trees give algae what it needs to grow. That is why the same spots turn green again and again.
How to Remove Algae from Concrete Step by Step
1. Sweep the area
Clear leaves and debris so the cleaner reaches the surface.
2. Apply an algae-killing cleaner
Wet nearby plants first, then apply the cleaner evenly over the growth.
3. Let it dwell
Give it a few minutes to work, but do not let it dry on the surface.
4. Wash with a surface cleaner
A rotary surface cleaner gives an even result without stripes.
5. Rinse well
Rinse the concrete and surrounding plants thoroughly.
How to Keep Algae from Coming Back
- Adjust sprinklers so they do not soak the concrete.
- Trim branches to let in more sun.
- Fix low spots and drainage where water sits.
- Schedule cleaning once or twice a year for shaded areas.
Pool Decks and Patios
Algae on pool decks is a safety issue as much as a looks issue. See how to clean a concrete patio and pavers for tips on pool decks and pavers.
When to Call a Pro
Large areas, pool decks, and stubborn growth are faster to handle with professional equipment. We offer driveway washing and patio and pool deck cleaning across DFW. Driveways usually run $150 to $300. For stains like rust or oil, see rust stains on concrete and oil stains on concrete.
Ready for a quote? Call 817-580-9881 or request a free estimate online. We serve Arlington, Fort Worth, Dallas, Grand Prairie, Mansfield, and the rest of our DFW service areas.
Related: Sidewalk cleaning
FAQs
What kills algae on concrete?
A cleaning solution made to kill algae, applied before washing. Pressure washing alone removes the surface growth but often leaves the roots behind.
Why does algae keep coming back on my concrete?
Shade, sprinkler overspray, and poor drainage keep concrete damp, which lets algae regrow. Fixing moisture problems slows it down.
Is algae on concrete dangerous?
It can be. Algae makes concrete very slippery when wet, especially on pool decks, steps, and walkways.
How often should concrete be cleaned to prevent algae?
Once or twice a year works for most North Texas concrete. Shaded or damp areas may need it more often.
