How to Keep the Algae From Coming Back
Cleaning removes the existing growth, but reducing moisture can help slow its return.
Try to:
trim shrubs and branches away from
the house
improve sunlight and airflow around shaded walls
keep gutters and downspouts clear
repair leaking gutters
redirect sprinklers away from siding
rinse pollen and dirt from shaded walls occasionally
Keeping the surface drier makes the environment less favorable for algae.
How Often Should Siding Be Cleaned?
There is no fixed schedule for every home.
A sunny, dry wall may remain clean for years, while a shaded wall in a humid environment may develop green staining much sooner.
Inspecting the siding once or twice a year is usually enough to catch algae before it becomes heavily established.
One Important Detail
Green staining is often algae, but dark or fuzzy growth can sometimes be mildew, mold, moss, or another type of biological growth.
If staining keeps returning unusually quickly, covers a very large area, or appears to be associated with water entering the wall, investigate the moisture source rather than repeatedly
cleaning the surface.
The Bottom Line
The easiest way to remove green algae from siding is often not aggressive scrubbing at all.
Apply a siding-safe cleaner, give it enough time to loosen the growth, gently brush only where necessary, and rinse thoroughly.
The real secret is contact time rather than force. Once the cleaner has done its work, much of the algae can often be removed with surprisingly little effort.
