The two or three places I've had a problem, I figured they came back after the first cleaning because they had their own "smell" and it was "home" to them.
So, I spray chlorox bleach full strength after the first cleaning, and they don't (haven't yet) come back.
When I had to clean up some racoon "dump" on my deck, I noticed the coon would come back to the same spot time after time. So I started putting chlorox bleach on those 'spots' and that also worked until they picked a different spot. A couple years now, have had no problem on the deck.
