How can I repair badly stained wood floors?

Have you tried mopping with something like Murphy's Oil Soap? It's for cleaning wood and it's very gentle on wood furniture and floors. You might also try putting a rug over the most heavily-trafficked areas in your house to help prevent the stains.

If the stains are black, they have penetrated the finish. You'll need to sand the finish off. You can try to sand the stain, if it isn't too deep or try a bleach treatment, left on for several hours. Then refinish. It may be worth your while to rent a sander, if there are large areas that need treatment. I did read that baking soda applied to the stain will help to neutralize the urine, but have not tried that. It's cheap enough to experiment, right?

I rescued for 30 years, so I feel your pain in that my pine floors are gouged beyond repair. I seemed to get all the hooligans, lol. Crate training is a must for housebreaking quickly and it saves your sanity, as well as the adopter's. If you need some tips, I'm here to help.

There are lots of ideas here that might be able to help you:

https://www.hometalk.com/search/posts?filter=stained%20wood%20floors

Wood bleach will help, but that’s part of the refinishing process.

Yes, rent a floor sander, as I can personally tell you that a hand held belt sander will be extremely tedious and has a high risk of a less-than evenly smooth finish.

Use oil-based polyurethane made for floors, at least two full coats.

This is messy and odorous project for winter and you’ll need to put up plastic “zip walls”.

You can sand the floor and restain, but this is a huge undertaking. Maybe some area rugs will prevent further damage.

Hope this Helps! Jeremy - https://do-daddy.com