Grandpa Chuck writes:

There is probably a better NG to post this in, but I don't know where
it is.

We have two cats. They use their large litter boxes in basement just
as they are supposed to. However, one or both of them also urinates on
the floor up against the wall and the lowest step going down to the
basement. We have never been able to catch them doing it - just the
wet spot with the strong urine odor.

One of our cats is a neutered male and the other a spayed female. We
just don't know what to scrub it with what to use to keep them from
doing it. The spot is only about five feet from the nearest large cat
litter box. We use the clumping litter and completely change it when
it takes on a urine odor.

Do any of you cat lovers have a suggestion that has worked for you?

We had that problem with our cat a couple of years ago.

You must remove the odor.
If it's still there, to the cat it's a bathroom.

I found just putting newspapers down (while it still smelled)
stopped the cat from using the area. Moving the box there
might work the same way for you.

In our case it was a carpet, eventually I replaced the carpet,
cleaned the floor underneath and sealed it with shellac primer.

I keep her box a bit cleaner and she hasn't gone back to
using the carpet.