Green algae on siding is super common — especially on the north side of houses or in humid areas. The “0 effort” trick people usually share is a spray-on, no-scrub solution that does the work for you.
Here’s how it typically works (and how to do it safely):
🧪 The Easy Spray-On Method
What You’ll Need
- Liquid laundry detergent or
- Oxygen bleach (like OxiClean)
- Warm water
- Garden sprayer (pump sprayer works best)
- Garden hose
✅ Option 1: Oxygen Bleach (Safer for Plants)
Mix:
- ½–1 cup oxygen bleach
- 1 gallon warm water
Steps:
- Lightly rinse siding with water.
- Spray solution generously on algae areas.
- Let sit 10–20 minutes (don’t let it dry).
- Rinse off with a hose.
✨ Algae usually disappears without scrubbing.
✅ Option 2: Mild Detergent Solution
Mix:
- A few tablespoons liquid laundry detergent
- 1 gallon water
Spray, wait, and rinse.
⚠️ If Using Bleach (Common “Neighbor Trick”)
Many people use:
- 1 part household bleach
- 3 parts water
- A small squirt of dish soap (helps it stick)
It works fast — but:
- Cover or rinse plants first
- Wear gloves and eye protection
- Never mix bleach with ammonia or other cleaners
Let sit 10 minutes, then rinse thoroughly.
🚫 Avoid
- Pressure washing at high pressure (can force water behind siding)
- Metal brushes
- Strong chemicals on aluminum siding
💡 Pro Tips
- Clean on a cloudy day so solution doesn’t dry too fast.
- Start from bottom and work up (prevents streaking).
- Rinse from top down.
If you tell me:
- What type of siding (vinyl, aluminum, wood, fiber cement)?
- How heavy the algae is?
- Whether you have plants nearby?
I can give you the safest exact formula for your house.
