Ivy says:
I was speaking with a neighbor recently who was having problems with her cat peeing all over the house. I asked her if she had take the cat to the vet to rule out a kidney infection and she said she had. The vet had suggested she buy more litter boxes.
She thought this was a stupid suggestion. “I have one cat and one litter box, how many do I need?” I told her the general rule of cat boxes is to have one for each cat plus an extra, especially if you live in a multi-level house as she does.
You should have at least one cat box per level* even if you have 3 levels and only one cat. For some unknown reason, cats are generally very fastidious about their pottying, but they will take a dump in your freshly folded laundry quick as a wink if their litter situation is not to their exacting standards.
Some cats may not like the type of litter you’re using, or they might not think you’re cleaning the boxes fast enough to suit them. Keep trying different things and eventually you’ll hit upon the right thing.
As for my neighbor, I saw her tonight and apparently having a second litter box on the second floor has done the trick. Go me and my advice! 
*If you have certain floors the cat can’t access, naturally you don’t need a cat box on that level.
