Cat urine is one of the toughest challenges we see - and we're certified in odor control! Dead bodies being in the same boat...In urine cases, there is no option but to replace the affected surfaces - since replacement is by far the cheapest alternative, all things considered.
Laminate, underlayment, subfloor, wallboard and trim...it is far less 'costly' just to replace a 4'x8' sheet of wallboard (at $10), tape it and mud it ($3.50), sand it and prime it - than it is to spend the next few trips applying a variety of chemicals that may or may not eradicate the problem.
Cat urine is a complicated chemistry, moreso than dog - even in a simple case (it may contains acids, bases, enzymes, hormones, medications, dyes, proteins, organic matter and/or fats) to remove a single shot smell is sometimes a challenge. Add in an absorbent surface and/or repeated doses, the problem defies the best chemists.
Insurance companies just replace everything as they want to be guaranteed there'll be no come-backs a few weeks down the road, dragging their company name into the mud. So they go the 100% effective way and replace everything.
Ozone is another possibility - but in very limited circumstances. But requires no human presence and no plants...can destroy other things too, so it's not the best alternative.
Mostly the urine soaks the flooring and the underlayment - rarely the subfloor. But if that's an issue, replace board by board. And yes, a good paint job will have to be done too because after such a time, the walls have absorbed the smell and have taken on a funk of their own. Again, replace to be 100% sure. Are you saying you don't have a subfloor?
So, a coat of a premium sealer may get you by...but may not. :wink: