Let me first say that I am a cat and dog person and have one of each. I also have NEVER had a problem with any of the cats I have had peeing on the floor or rugs. I have had litter boxes on my carpeted area and now on my hardwood floors. That being said, I have a covered litter box 'house' type of litter box, and my cats have always been female. Sounds like the person whom you bought your house from may have had cats with behavioral problems, or the cats may have suffered from reoccurring UTI; so please don't think all cats urinate on the floors!
That being said, my sister had a problem with one of her cats who constantly used the house as a litter box. Her house did smell like urine. Cat urine if very concentrated, which the why the smell is so strong. And, cats have a tendency (like dogs), to return to the same spot to pee again. The urine contains crystals that reactivate when wet again. Regular cleaners or shampooers will not do the job. The only thing that will remove the smell is a neutralizer like Natures Miracle, which is sold at stores like Petsmart, will do a good job of removing the smell. I have a feeling the owner may have tried to clean the stains by over-saturating the rug with cleaner, hence the large stains on the floor base. I would first try saturating the rug with the odor neutralizer, putting a heavy towel underneath the carpet pad. Let it dry and re-shampoo. Good luck with this, it worked for my sister.

Here is a link that might be useful: cat urine removal

You said you were " wondering about the sheetrock around this area." I know it could be a problem even though it isn't stained. Ask about primers/sealers at the paint forum. Klitz is a good one, but I don't know if it would do the trick- better to be safe. My daughter had the same problem and she ended up replacing the sheetrock- about 18 ins. at the bottom.

Thanks for the input, y'all. I spoke with our flooring guy and he said that he would definitely replace the underlayment that is stained and stinky (I think that's what it is called - the board above the subfloor) and the subfloor if it is also stained. I guess that the urine basically went straight through the carpet and pad and that's where it's trapped. The smell is honestly unreal. This room is beside the garage, where we parked our car for an hour today, and when we left our car had the smell inside. I didn't know that about the crystals. They probably did use a lot of cleaner and water trying to get rid of the stains and smell. I'm going to pursue replacing the subfloor and pad in the upstairs room in the corners where the cats peed and hope we can clean the carpet well an the smell will be okay so we don't have to replace that carpet. I don't know much about cats but I'm sure that not all cats act like this or no one would want to go through it. :)

Our painter doubts the sheetrock is affected because cats pee straight down so he's not sure it could get into them. I really hope he's right. Something I read somewhere mentioned using a black light and trying to see if there's any urine in the sheetrock but I don't know anything about how to do that.

You can get a small, cheap, battery-powered black light at any pet store. Wait until it is dark, turn the light on and look for places that glow. Glowing spots are contaminated with urine. Other things, such as blood or semen may glow as well (just don't take a black light to a hotel room - you'll never sleep after you see how everything glows)

PS they sell the blacklight at Petsmart in the aisle where the Natures Miracle is sold. I have one of those (not for the urine reason however), and they do work. The OP is correct, they are only a few dollars.

Before you rip wood out try kilzing (oil based) the area then give a few days to let the Kilz odor out and see if its better.

cat urine can come close to destroying a house..
If the odor lingers and can be detected, no one will risk the purchase.
People have so many cats and dogs, and then do not clean up to the letter of the book and cannot afford professionals....
A problem, no solution??
These forums help, but who cannot read are in deep do-do.

We had a cat who sprayed. When we replaced the carpet (after the cat died), we Kilzed the spots on the sub-floor that looked like it may have pee on it. This was 10_ years ago and no one has ever said my house smells like cat pee.

Thank goodness we have a new kitty now who has no problems.

My experience with cat urine is you have no choice but to remove the carpet and the pad. As for the wood flooring...I'll tell you my recent story.

We've had a faint bad odor for years and depending on certain weather it became more annoying. Couldn't figure out where it was coming from.

Once we began our renovation and tore the walls out, we discovered two squirrels nests in the living room walls in two opposite corners. The smell was putrid and unbearable!

We tried what the exterminator recommended.

1. Natures Miracle...poured the stuff on every day for a week. Did nothing.
2. Straight Bleach sprayed every day for two weeks. Did nothing.

We're getting worried now because our insulation is getting ready to go in.......

After some research, I think we've found the Miracle Cure!!!

***KILZ Original Oil-Based Stainblocking Primer & KILZ Upshot

I first THICKLY hand painted the KILZ original, and for the nooks and cranny areas that I couldn't reach with the brush, I used KILZ Upshot Spray. I've done this two days in a row now. For the first time, I can't smell a thing, when I walk into the closed house.

To finish off, I'm using another oil based product:
BIN by Zinsser Shellac Base Primer-Sealer- Stain Killer a polyurethane Wood Sealer on top of the KILZ to make certain

....and we've sealed the entire area to keep the critters out in the future.

Best of luck to you and hope this helps!

Here is a link that might be useful: KILZ Original and KILZ Upshot

I would replace the subfloor (all the way down to the floor joists) and the drywall up a few feet. Just to be safe. Better to do that than learn after the floors are in that you still have a stink.

I've never had a cat that peed on the floor. One elderly one was partial to the bathtub, though. Ours is on a concrete floor. I would never put one on carpet.

Cats do have a smelly urine and it does have strange chemical characteristics that can be controlled. In the case of the OP, it would be too time consuming to remove the urine from the underlayment so, replacement would be the best way to go there. I would also suggest using Kilz on the joists to seal them off. You could also use a couple of coats of Poly Urethane for floors to seal the wood off. I agree, the previous owner did what most people would do and that is saturate the area with water in an attempt to clean up.

How to clean and neutralize cat urine....As a previous poster said, the cat urine contains crystals and this is where the problem is. The idea is to get to them as soon as possible although that is not always possible, especially with older cats who have accidents in places you are not aware of. Use straight ammonia on the area and LET IT DRY completely. The ammonia will react with the cat urine and crystals which will create a new type crystalline substance. Yes, you'll have to deal with the ammonia smell and cat urine for the moment but it will be worth it at the end of the day. The important part and the one most people are apprehensive about is to LET IT DRY. That is the only way the chemical process will complete. Once dry, vacuum the spot thoroughly to remove the crystals from carpet or cloth material. Re-treatment is usually not necessary. The process works especially well on dried cat urine. If it makes you feel better to treat the spot one more time, wait a week or two. Once everything has been vacuumed and totally dry, sprinkle some baking soda on the spot, let it sit for a day and vacuum that up. You can lay your head there and sleep on it with no odor (or trace of urine)if you are so inclined to recline!!!!

Seen too many properties with this problem and itâÂÂs nasty. Every cat owner will swear their home doesnâÂÂt smell but I have never been in a home that I couldnâÂÂt tell had a cat. IâÂÂve been in hundreds where it was noticeable but the owners still believe itâÂÂs not a problem.

Cat urine is far more concentrated then dog and human urine. A cats kidneys are so efficient at extracting absorbable water that the high concentration makes the urine extremely foul.

With that high concentration, the real problematic component of cat urine is uric acid. This concentrated acid causes that nasty odor and makes stains hard to remove. Uric acid contains non-soluble salt crystals which bond like crazy glue to any surface. These crystals bond to wood, drywall, grout, ceramics, marble and even concrete.

Even when the crystals are dry, the problem remains. Any moisture will reactivate the crystals releasing the smell all over again. Usually the smell gets worse since the crystals concentrate after drying. Humid summer days will reactivate the problem years after the cats are gone.

The only way to resolve the problem totally is to get rid of the carpet and pad. If wood subflooring needs replacing due to the urine damaging the integrity of the plywood, replace those areas. The rest of the subflooring needs to be thoroughly cleaned, dried and sealed with Binz.

YouâÂÂre not cleaning the subfloor to get rid of the cat urine but to make sure you have a clean, dry surface for the Binz to adhere to. The Binz shellac primer will seal down to a .005 microns which is critical. Kilz only seals down to .015 microns so I recommend Binz to fix it the first time.

Any walls or trim that are suspect to the urine also needs to be sealed with Binz and repainted. Even concrete needs to be cleaned and sealed but I recommend using and epoxy on the concrete if itâÂÂs going to be left exposed.

The biggest lesson I learned is if a cat is urinating frequently in a few areas of the home, itâÂÂs likely a problem throughout. I purchase properties for investments and if IâÂÂm looking at a property with cat issues, I figure replacing the carpet and pad in all rooms, cleaning and sealing all the floors, sealing half way up the walls, repainting entirely, sealing (sometimes replacing grout and/or ceramics) and even having the duct systems cleaned as this odor permeates all areas and cats will even urinate into the floor vents.

The last property I purchased like this had the price reduced $35,000.00. I cost me $40,000.00 when I was done so I should have reduced the price $55,000.00 as my intent is to be profitable and this is a horrible problem.

I have read all the comments above as we are remodeling and are needing to replace the carpet and floor not only because its part of the remodeling project but also because my cat suffered from a UTI and completely ruined the carpet in the hallway. Anyhow, I was wondering if any of you that have suggested to use Kilz if you know if there are any health risks from the use of it? I am trying to get pregnant and didn't know if it would cause any harm or if it can cause cancer or any other health conditions? If so, do any of you know of any natural based products you can use? I have used Nature's miracle and have spent a lot of money trying to get rid of the smell and finally gave up and just covered it with plastic runners. Any suggestions or comments would be very appreciated! Thank you!