I was practicing on cedar shingles on my friends woodshed. It was pretty bad with a lot of tarpaper showing. Anyway I rinsed it off with the garden hose and it took a long time to do 150sq'. if that were a real job on a real house, no way would I be making any money. I have a 4gpm 4000 psi, but that would probably rip things apart pretty good. I was thinking maybe a small machine at 5 gpm and 1000 psi for a good rinser.