People often ask me why one wall looks fine and the wall around the corner looks like it belongs to a different house. It is almost always the north side, and there is nothing wrong with your siding.
It is about how long the wall stays wet
A north-facing wall in Georgia gets very little direct sun. After it rains, or after a heavy dew, that wall stays damp for hours longer than the south side does. Algae does not need much — moisture, a bit of shade and something to sit on. Give it a wall that never fully dries and it will take it.
Add our tree cover to that and it gets worse. A lot of Forsyth County homes back onto woods, and anything sitting in shade all day behaves like a north wall whichever way it faces.
What that green actually is
Mostly it is gloeocapsa magma, an algae, sometimes with mildew and lichen along for the ride. On siding it is a surface problem for a while and then it is not — lichen in particular puts roots into the surface, and by then you are cleaning damage rather than dirt.
It also holds moisture against the wall, and that is the part that matters. Constant damp is what shortens the life of siding and paint. Washing it is maintenance, not decoration.
Why pressure is the wrong tool
Blasting it off with high pressure looks like it works. It knocks the green off, the wall looks clean, and it is back within months because whatever was rooted in the surface is still there. Worse, high pressure on siding drives water up underneath the boards, where it has no way out.
Soft washing does the opposite. Low pressure, the right cleaning solution, and time to let it work. It kills what is actually growing, so it stays clean far longer, and nothing gets forced anywhere it should not be.
If one side of your house is letting the rest of it down, call or text me on (770) 789-1606.