We replaced the sub floor because even when we replaced the flooring and scrubbed the sub floors the smell never left. Esp. in warm weather! SO glad we did replace the sub floor although I will never get another cat.

Is it a difficult job to replace sections of the subfloor? Something a somewhat handy diy'er could accomplish?

No! Its not difficult! If you can run a skill saw you can do it! You dont even have to be good with the saw although it helps :).

What kind of subfloor? Ply? Pine plank? Osb?

It will require some muscle and sweat to remove the old depending on the type and if its screwed or nailed and if theres glue.

Agree, easy.

Cathy...I've been through an entire house of cat pee. I feel like I'm an expert.

The worst case is to rip out the subfloor and replace. Before you do that, if you have a solid (non OSB) subfloor, you can try a less invasive method:

1. Buy Thornell Cat Odor Cleaner (you can find it on amazon)...they make Kennel cleaning products, and the cat is more concentrated than Kennel Odor Cleaner.
2. Dilute properly, then take a spray bottle and really soak the spot, subfloor, cracks between subfloor pieces and ideally, the underside of the subfloor (if you can get at it).
3. Let it dry and the smell disspate. Repeat several more times until the smell is 99% gone (and smell test on a super humid day, without AC as humidity activates the ammonia in the cat pee).
4. Seal the subfloor with 2 coats of polyurethane (you want something waterproof so the humidity can't get at the wood).
5. After the poly smells dissipate, smell test again on a super humid day (preferably, leave the house over a weekend, closed up, no AC when it's super humid out).
6. If you can't smell it, you win!
7. If you still can (or your floor is OSB), rip and replace.

Good luck!

ITA with navi_jen. My product of choice is Nature's Miracle Cat Urine Destroyer. Also Amazon, see link. You spray it on straight. Never had it fail me.

So sad when this has to be addressed. A clean litter box and a caring pet owner could have avoided this 95% of the time.

Here is a link that might be useful: Nature's Miracle

Cathy - Am glad you have a sense of humor. Also, glad you found the floorboard replacement easy - and you will always have cats!

MizLizzie - cats often present with inappropriate urination as a sign of an underlying medical condition, including cystitis, diabetes, and hyperthyroidism. Unfortunately, all of these are VERY common in cats. If only we could teach our kitties to tell us when they are having dysuria or palpitations. Maybe, ''meow, meOW, MEOW.'' :-)

I found this very helpful even 6 years later. Thank you, my cat has had some major medical issues and her urinating in this spot was how she told me or I would have never know.

Hello to anyone that can help us. We acquired a home that has had many cats maybe 30 or so at one time so I am told and the carpet has been ripped up and the concrete subfloor and stairs and upstairs hallway wreaks of cat urine! I cleaned many times to prep for new carpet and all but the smell is back in a day or so. Help! I know the plywood can be replaced but what about the concrete slab throughout the home? Any suggestions? Desperate seeking solutions! The house is lovely otherwise.