Green algae on house siding is common in damp, shaded areas. While no method is truly “zero effort,” there are effective ways to remove it with minimal scrubbing.
A simple approach
- Rinse the siding with a garden hose to remove loose dirt.
- Apply a cleaning solution. Common options include:
- A mixture of 1 part household bleach to 3 parts water, plus a small amount of dish soap to help it cling to the surface.
- An oxygen-based cleaner if you prefer an alternative to bleach.
- Let it sit for 5–10 minutes. Don’t allow the solution to dry on the siding.
- Rinse thoroughly from top to bottom with clean water. Most algae should wash away with little or no scrubbing. Stubborn spots may need a soft-bristle brush.
Safety tips
- Wear gloves and eye protection when using bleach.
- Protect nearby plants by wetting them with water before and after cleaning.
- Never mix bleach with ammonia, vinegar, or other household cleaners, as this can produce dangerous gases.
- Test the solution on a small, inconspicuous area first to make sure it doesn’t discolor the siding.
What about pressure washers?
A pressure washer can speed up the job, but using too much pressure may damage vinyl siding or force water behind it. If you use one, choose a low-pressure setting and keep the spray directed downward rather than upward under the siding.
Cleaning the siding once a year and trimming vegetation to increase sunlight and airflow can help reduce algae from returning.
