Curious what kind of 'cartridge respirator' that would have to be. There are various filters for different purposes. A particle filter is useless for odors. Possibly a carbon filter designed for organic vapors like solvents would work. Try it and see. Ammonia may come through but it should kill most of the odor. They make other filters for acids and bases and such. Ammonia is a base.

You might be able to seal drywall with a primer like Kilz that is designed to block stains from soaking through. I don't know how effective it is for urine odor but it forms a pretty impermeable barrier. I would think the amount you're trying to block on a wall where it has just penetrated from the air will be quite a bit different from a floor actually soaked with urine, which you'd have to remove.

Consider renting an ozone generator for a couple days after you've gotten the floor materials out, just to treat residual odors. You can close up the house and let her rip.

Thanks for the tips. I was thinking about an ozone generator at the end of any chemical/sealer processes.

We successfully removed cat pee odor from our basement - had to pull up the tile and then seal the concrete underneath. Used Kilz. Then painted the cement floor. Had to pull up the baseboards and throw them away.

My grandmother's house on the other hand... her cat peed in her basement and years later the smell still lingers.

Good luck!

I'm still finding spots in my basement where my cat peed on the rubber-backed carpet squares before she went to kitty heaven a couple years ago. Behind furniture and such. I wondered why our neighbor's cat, who thinks it can live at our house too, will make a beeline for the basement whenever it gets into our house. Silly cats. :-D

if it was really bad it could get into sub floor and even the joists beneath would have to be sealed with odor blocking primer. I once saw a house both before and after some guy did a half arse job with it and I could still smell the pee mixed in with the smells of the newly applied wood floor finish. It was the kind of thing where you might not notice it at first....unless, like me, you knew its history. I dont know if Id want to deal with it - if I did I would certainly plan for absolute worst case scenario, and price my offer accordingly.

Keep in mind the construction and materials in the house. We had one room where we had to rip out and remove the carpet, pad and the tack strips, remove the base boards, cut and remove the bottom 2 feet of sheetrock. The we removed the insulation behind the drywall. With everything removed, we sprayed the studs and concrete slab with a bleach solution to sanitize, then and enzyme cleaner to deodorize (might have been enszyme then bleach -- been years now). Then we painted the slab and any surfaces that were in question with KILZ. We put up new insulation, new sheetrock, new baseboards, primed and painted then put down a new wood floor. Never had an issue and was well worth it. But that was only one room.

If the smell is that strong, you may have a hard time knowing where it is all coming form and just how much you will have to do. Assume more rather than less. If you have a wood subfloor, you might have to remove and replace sections of that, and the smell may have permeated areas that were not hit by urine. Factor in whether you can do some or all of the work and the cost of that against how good a deal you are looking at on the house.