How to Remove Algae From a Patio

Updated February 21, 2017

Algae require wet or damp conditions to survive. It grows on patios and other structures around a home that has adequate shade. Overgrown trees and shrubbery cause excess shade on the patio and allow the surface to remain damp, making it a perfect growing environment for algae. Algae can make the patio slippery, resulting in a hazardous situation. The slimy green growth also takes away from the patio's aesthetic appeal.

Trim overhanging bushes, flowers, grasses and trees. Trimming the growth will allow more light to shine on the patio, which will help to eliminate an algal environment.

Pour equal amounts of chlorine bleach and water into a spray bottle or mix ammonium sulphamate with water according to the package directions. Ammonium sulphamate is an herbicide, found at gardening supply stores.

Apply the mixture of your choice to the algae and allow it to sit for 30 to 60 minutes.

Rinse the patio thoroughly with plain water. Direct the stream and flow of water away from any vegetation that you want to keep. Ammonium sulphamate is not exclusive to algae; it will kill any plant it meets. Repeat the treatment if necessary.


Wear safety glasses and gloves when handling chlorine bleach or herbicides. Keep trees and bushes trimmed to prevent future algae growth.

Things You'll Need

  • Chlorine bleach or ammonium sulphamate
  • Spray bottle
  • Garden hose
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About the Author

Sal Marco began writing professionally in 2009. He has written many online home improvement articles based on his more than 20 years of experience in the home improvement and building industries. He has worked as both part of a team and as a site supervisor. Marco has a Bachelor of Science in management science from Kean University.