We bought the house from the original owners in 1996. At that time the siding was already on it. It was fairly new though, so I don't believe the first owners ever washed it, and we have never washed it before either. I know the marks were not there before this cleaning. I have pics of the house of course, but probably not close up enough to show that the siding was undamaged. Never anticipated this problem so didn't think to take close ups so most photos are at a distance. I'll have to go through my pics and see what I can find.