About 45 years ago, the place I first started working at, was putting a sign on the face of a building. It was a flat roof (slight slope, of course) and we boomed the big stuff up onto the roof. Got the signs up and everything looked honkie-dorie when we left. About a week later, the boss got a call. The store owner has a leak in his roof. We got blamed because we were supposedly the only ones up there in the last 10 years. Yeah, right. Turned out, the 2 leaks were wa-a-a-a-ay in the back of the building. Not anywhere where we had been, at least 40' away from where we were. He still hadda pay to fix the roof. I still think it was an old leak and he jut did that to get us to pay for it.
That is the reason I have a clause that simply states.... we are not responsible for any leaks old or new related or not related to what work we are performing. It has other items in it like cracks or electrical problems and we tailor it as needed.
Had a guy once tell me he was gonna sue me, because we had left some dirt on his property after digging 6 huge holes. This was some leftover dirt nuggets about the size of a peach pit sprinkled around in his grass. I had him come out and show me these mounds of dirt he was complaining about and he showed me these little specs of dirt. I told him to be careful as he might trip over one and brake his frickin' neck, if he ain't careful. I stepped on the pieces and left 10 minutes later. Since then, I now put a huge tarp of cardboard down and we take any dirt away when finished.