I have used with great success "Out" pet stain and odor remover spray purchased at WalMart. It's a milky liquid that has no smell but removes the odor of whatever you spray it on. I have used it at our hunting cabin on tough odors (mice) and mustiness as well and a few hunters along the way... Saturate your problems areas carpet and all. It's an enzyme like others have suggested. Works on stinky drains and refrigerators, too. Also, Oil of Wintergreen in a 3 to one mix with water can be sprayed on your concrete and carpet, recommendation from a carpet installer years ago. The former owners of our house had a dog that urinated frequently indoors. The Oil of Wintergreen neutralized the concrete odor with amazing results.

If the slate looking tile is "hard slate" or "porcelain" it is not very porous. If it is "soft slate" is is very porous. Regardless of what the tile is made of, the grout will soak up urine/poo and it is impossible to get it out. Grout that is mixed/poured right will be less porous. However, the soupier the grout the easier to install, then the owner is left with lots of pinholes where the air bubbled out. Drop a few drops of water on the "tile" and see how fast it absorbs. If it sits there in a puddle, the tile is not porous. I would think covering the tile/grout with the enzyme for getting rid of urine would make a difference for the better. No amount of scrubbing will get the odor out of the grout.

The smells you are used to living with will never bother you (hmmm -- except maybe in extreme circumstances when the odor sucks all the oxygen out of the room! Yes, I was in real estate and experienced that.) You may think your cats ALWAYS used the litter box but obviously, others know better. Dogs aren't so bad because they don't spray the walls BUT they can also smell if you don't let them out and bathe them often enough. As far as wood floors go, you can't sand out cat urine. It will be there as long as the floor stays. Sorry --- you enjoyed your pets and this is the price. You will finally sell your house at a discount because you enjoyed those pets. Someone buying your house may have to replace drywall and floors and will expect you to pay for that. Sad but true.

We bought a house from heavy smokers who kept their house pretty clean. We thought we could get rid of the smoke smell by cleaning everything really well and airing the place out, either cleaning the window treatments or getting rid of them, either cleaning the carpets or worst case replacing them. Turns out we had to clean and air the home, scrub the heck out of everything, replace the nearly new carpet, throw out the window treatments, repaint all the walls and ceilings, and replace some of the drywall. Also, the smell of the cigarette smoke masked the musty odor of the home. Once we got rid of the cigarette smoke, we had to find the source of the other odors and fix those. I don't think I will ever, ever buy another house that doesn't smell fresh unless I have no other choice. Our neighbors bought a home from owners who had a cat who urinated on the floors. They wound up having to replace the subfloor. I think they said they'd never ever again buy a house that smelled of cat urine. I hope whatever you decide works for you!