This is the part that makes the method feel almost effortless.
Instead of immediately scrubbing, allow the cleaner to remain on the surface for the amount of time recommended on the label, often around several minutes.
As it sits, it begins breaking down the algae and loosening its grip on the siding.
Do not let the cleaning solution dry completely on the wall.
Step 5: Gently Brush Stubborn Areas
Light algae may rinse away without scrubbing.
Older or thicker growth may need a
little help.
Use a soft-bristle brush and gently work the affected area. You usually do not need heavy pressure once the cleaner has had enough contact time.
Avoid wire brushes or very abrasive pads, which can scratch or damage siding.
Step 6: Rinse Thoroughly
Rinse the wall thoroughly with clean water from top to bottom.
Continue rinsing until no cleaner or loosened algae remains.
Once the siding dries, the difference is usually dramatic.
Why I Wouldn’t Start With a Pressure Washer
A pressure washer can clean siding quickly, but more pressure is not always better.
Used incorrectly, high-pressure water can:
force moisture behind siding
damage paint
mark softer materials
loosen panels
damage caulking around windows and doors
For ordinary algae, allowing an appropriate cleaner to do most of the work is often safer than trying to blast the stain away.
If you do use a pressure washer, follow the siding
pressure.
What About Household Bleach?
Diluted chlorine bleach is sometimes used for exterior algae and mildew, but it requires extra caution.
It can damage plants, discolor some materials, irritate skin and eyes, and create hazardous fumes if combined with incompatible cleaners.
Never mix chlorine bleach with vinegar, ammonia, acids, toilet cleaners, or other household chemicals.
For routine cleaning, a purpose-made siding cleaner or oxygen-based product is often easier to use safely.
Don’t Forget to Test a Small Area
Before treating the entire wall, test your cleaner in a small, inconspicuous spot.
Wait for the area to dry and check for:
discoloration
fading
paint damage
surface changes
This simple step can prevent an expensive mistake.
