Green or Black Algae on Your Driveway and Sidewalk: Causes and Fixes
Concrete that stays shaded and damp, especially on the north side of a house or under trees, often turns green or black. That's usually algae or mildew growing in the surface.
Why it grows here
Middle Tennessee's humid summers and shade from trees and houses keep some concrete damp for long stretches, and that is what algae needs.
Why it matters
Growth can make walks and steps slick when wet, and it comes back faster if only the surface is rinsed.
How it's cleaned
Surface cleaning lifts the growth evenly, and a post-treatment helps slow regrowth. Sealing can also help concrete shed water.
What you can try yourself
- Trim branches to let in more sun
- Point downspouts away from walkways
- Sweep leaves off concrete so it dries out
What to avoid
- Wand-only pressure washing, which can leave zebra stripes
- Walking on slick areas in wet weather before they're treated
When to call a professional
We clean shaded driveways, walks and steps and treat them to slow regrowth. Send a photo for a quote. See our driveway & concrete cleaning service.
What customers say
"I used First Class Pressure Cleaning to seal my aggregate driveway and they did a fantastic job. It was in rough shape as we had never sealed it before. Lots of salt damage as well from trying to de-ice the last winter storm. It looks so much better now. They even came back the next day for touch-ups on some areas where the winter salts had worn through to the concrete. Very happy with this company and the work they’ve done!"
Dan · Google Review
"Driveway looks amazing. Very surprised at the results. Team was very easy to work with. Excellent communication. Fair price. Let’s hope it holds up for a few years."
Mothball K. · Google Review
"I completed a quote sheet online for an estimate to pressure wash my house. First- Clean Pressure Washing responded quickly. Chris called me to discussed what service I need. He looked at my house on the Internet so he was able to see clearly the size of the house. I also added my driveway to the cleaning process. I was given a quote, verbally and written, which I signed on a DocuSign. They communicated with me via text and were right on time based on the schedule provided. They had a truck that had the solution in it for cleaning my house, which I was really happy about because they didn’t use my water. My driveway was really messy and they did a very good job on my house and driveway. I felt the quote was fair and competitive. They got all of the mildew off the house. It looks great so I shouldn’t have any problem with my HOA for a couple years. Thanks so much, Chris. I really appreciate the service you provided!!!"
Karla J. · Google Review
96 Google reviews from homeowners and businesses across Middle Tennessee. Read them all on Google.
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