She didn't say if the litter was being used for a cat or for other purposes that deal with snow. So cat litter won't ruin your furniture if its not being used by a cat, its just like sand. It's annoying to clean up, but thats life sometimes. Also her tattle tailing to management instead of going upstairs to her neighbors and talking to them about the issue rubs me the wrong way. I would understand if that person was being like "OH YES, LETS POUR SOME CAT LITTER DOWN THERE. HEY NEIGHBOR, HOPE YOU LOVE RAINING CAT LITTER." But she's not giving that kind of impression.
You are right. We don't know.
I don't know if my kids's socks and underwear are clean or not when it's laying all over their bedroom floor, but I'm not going to take my chances - into the wash it goes.
Same with this....I'm going to assume first that there is a litter box being used on the balcony and that is where the litter is coming from. I'm not going to take my chances with thinking that the litter might be clean....personally I would wash everything, cover it, and talk to the neighbors or mgt company, which is the advice I gave OP. But even covered, I still wouldn't want to deal with disgusting cat litter all over my patio and chair covers! If the litter happens to be laid down because the renters upstairs are super-safety conscious and have the good sense to lay down clean cat litter on their balcony so they don't slip and hit the railing when they step outside in the winter, then so be it.
Again, my response was specfically responding to the entire post of:
How was your patio furniture ruined by the cat litter? Can't you just wash it off? , not all of the what-if's. My answer to that, assuming the cat litter is NOT being used as an anti-slipping agent, is no, IMO, I cannot just wash off cat litter and be good with it falling all over my stuff if I were the OP. It would gross me out and I would want to throw my stuff away.
And - I don't care whether the OP covers her stuff...if it's on her property, she can do whatever she wants with it, with the reasonable expectation that cat litter, dirty or otherwise, will not be falling on it. Personally, if I lived in an apartment with a covered patio, I wouldn't spend the money buying covers for my outdoor furniture....the pieces are reasonably protected from the elements under the covered patio. Well, unless, apparently, the upstairs people have a cat. (or are very worried about slips and falls).
But whatever. Not everyone will agree. It's OK.