when I had litter box issues, the guilty party was confined by themselves, with a litter box with Cat attract. As soon as litter box habits started going back to normal, I would allow supervised visitations out of the room. Just kept doing this until he was trustworthy out in the house, and it never happened again. But you are correct that if the uirine has soaked into the subfloor, it will have to be cleaned and primered probably. The cat can still smell it, even if you get it clean enough that you can't. And my cats loved thecat attract litter, so much so that they slept in the litterboxes.