My cats miss the litter box so urine gets on the floor. The only way to keep urine from leaking outside of box is to put a towel in the bottom under the cat box. It gets urine soaked and I change it 1-2 times per week.
The height of the box for the cats is too low. I keep the lid open. They can use it if I close the lid but who wants to pee in a bathroom built for a midget.
The extra wall is great in keeping 90% of the litter inside and not tracking.