This morning, before 11, I heard someone doing building in the next-door building. I thought it was weird, but didn't do anything about it.
This afternoon, I looked out the window, and there was a lot of brick and mortar on my (flat, crap) roof, and a pipe running from the next-door building through the newly-broken grate on my roof .
I was furious, and ended up going around, with two under-dressed children (DH) away, to say, more or less 'oi, that's my roof, wtf?!?!'.
At least they were apologetic, but they said, oh, we didn't have plans, we thought that was communal. I mean, ok, the next-door building is leasehold (they did try to tell me that my roof was communal - said, oh, do they come clean it out ... no. because it's my fucking roof, we're responsible for it) but surely they need permission from someone else to change bits of it ...