Seems like every 2 yrs I have to clean the siding on the house, especially the north side and any other spot that doesn’t see direct sunlight.
While the effort is well worth it, the cleaning process brings it right back to new, but.. the power washer with the 18 ft extension wand can be brutal on the shoulders and arms after a while. There’s a product I use, made by Jeep, that in environmentally friendly and biodegrades (or so they say). It comes in concentrate form and a typical dilution of 4:1 will be strong enough to remove most material.
There is one type of mold, if it is indeed that, that will not come off until I pick at it either with a plastic tool or thumbnail. The closest description I can come up with is as if someone was spraying a car nearby with a burgundy color, and the overspray made its way to the house. Its all over the siding and I’ve even found it on the truck.
The house actually is not as dirty as seen in the photo. Once the solution is sprayed on the house, almost immediately the house starts to change to the murky color. Directions say to wait 15 minutes before starting back with the sprayer to remove it all, to give the solution a chance to break down the organics.
You can see the spots in the picture above, that’s the burgundy color mold that will not come off with the pressure washer.