How to Clean Algae off a Concrete Like a Pro

A concrete surface with algae on one side and the other side clean

Table of Contents

Algae can be a pesky problem for homeowners. It not only creates an unsightly green film on your concrete surfaces but can also make them slippery and dangerous. But worry not! In this guide, we’ll walk you through the process of removing algae from concrete surfaces like a pro.

Understanding Algae

Before we dive into the cleaning process, it’s important to understand what algae is and why it grows on concrete surfaces. Algae is a simple, non-flowering plant. Its species are ubiquitous, and they can grow on virtually any surface as long as the conditions are damp and there’s enough sunlight.

Concrete surfaces, especially those in shady, damp areas, are prone to algae growth. This is because concrete is porous, allowing algae to anchor itself firmly, making it difficult to remove.

Preparation for Cleaning

Proper preparation is key to effectively removing algae from concrete. Here’s what you’ll need:

  • A stiff-bristled broom or brush
  • Pressure washer (optional)
  • Commercial algae/moss killer
  • Bucket
  • Water
  • Protective gear (gloves, goggles)

Before you start, ensure you’re wearing protective gear. Algae can sometimes cause skin irritation, and the cleaning solutions used can be harmful if they come into contact with your eyes or skin.

Step-by-Step Guide to Cleaning Algae off Concrete

Now that we’re prepared, let’s get down to business. Follow these steps to clean algae off your concrete surfaces:

  1. Sweep the area: Use a stiff-bristled broom to sweep away loose algae and other debris from the concrete.
  2. Prepare the cleaning solution: Follow the instructions on your commercial algae/moss killer to prepare the cleaning solution. If you’re using a homemade solution, a mixture of one part bleach to ten parts water can work effectively.
  3. Apply the cleaning solution: Pour the cleaning solution onto the algae-covered concrete and scrub with a brush. Be sure to scrub vigorously to remove the algae from the pores of the concrete.
  4. Let it sit: Allow the cleaning solution to sit on the surface for at least 15 minutes. This gives it time to penetrate the concrete and kill the algae.
  5. Rinse: Rinse the surface thoroughly with water. If you have a pressure washer, this can be very effective at removing any remaining algae.
  6. Repeat if necessary: If there’s still visible algae, repeat the process until the concrete is clean.

Remember, safety first! Always wear your protective gear during this process to protect yourself from the cleaning solution and any flying debris while scrubbing or pressure washing.

Preventing Future Algae Growth

Now that your concrete is sparkling clean, you’ll want to keep it that way. Here are some tips to prevent future algae growth:

  • Improve sunlight exposure: Algae thrives in damp, shady areas. If possible, trim back overhanging branches or other structures that are blocking sunlight.
  • Keep it dry: Try to keep your concrete surfaces as dry as possible. Regularly sweep away puddles, and consider installing gutters or drains if water tends to collect.
  • Seal the concrete: Sealing your concrete can close the pores and make it harder for algae to take hold. There are many concrete sealants available on the market that can provide a protective layer against algae growth.

Prevention is always better than cure. By taking these preventative measures, you can keep your concrete surfaces algae-free and looking their best.


Cleaning algae off concrete may seem like a daunting task, but with the right tools and techniques, you can do it like a pro. Remember, the key is to not only clean the algae but also take steps to prevent future growth. With this guide, you’re well-equipped to keep your concrete surfaces clean and safe.

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