Can ruin a house faster than any dog. Pee cats (cats who pee outside the box) can do thousands of dollars worth of damage. I love my cats, but yesterday after cleaning out the room that we're going to use for Livvie, I could cheerfully have killed all of them, or even sold them for medical research.
All it takes is for one cat to get the stupid notion in his head to pee outside the box. This is why, for your own sanity, you should never place a litter box on carpet. After the first cat pees it's fair game for the rest of them. And here's the kicker, cat pee can be smelled but not usually seen, and those enzyme cleaners rarely work.
Yesterday I also discovered that anything box like had been fair game for pee as well. The cats went into the closet (!) and peed on boxes that were stored in there and destroyed 2 full boxes of books, a box of clothing, and two quilts that were folded up and stored in there.
We ripped up the carpet and found multiple areas where the pee had gone through the padding and saturated the hardwoods underneath.
Now we have to paint the floor with a sealant to lock in the bacteria and odor, paint the floor white instead of having hardwoods in Livvie's room, and repaint all of the walls (which we were going to do anyway).
And after all of this I will never ever have carpet again. Ever.