Ran deal with animal pee a lot at work..

First try this. Take about a tea spoon of bleach (unscented) and pour on the spot. If it bubbles. The urine is embedded in the sub floor (plywood). You have two choices.

#1. Soak the area with pure bleach and let it dry. Then Kiltz.

#2 replace that section of sub floor.

Check and see if the guys doing the work could "Core Drill" a section of the sub floor. By that I mean use a 3/4 to 1" hole saw and drill through the sub floor to extract a sample to examine. If it is good and solid. Bleach and Kiltz. If it shows signs of rot or that the glue bonding the sub floor has begin to or has failed. Replace it.

I core drill many sub floors to get a glance of their condition before i just up and cut one out. The hole saw that I use is just slightly smaller than a Gatorade bottle cap. I use the caps to place down into the hole and then fill it with epoxy for a repair. I get laughed at a lot for core drilling sub floors by people in the business. But have yet to hear one homeowner laugh when I saved them a wad of cash and stress from having their floor ripped up for no good reason.

Cheapest first try would be to flood that area with Nature's Miracle. Get the surface wet and let dry(24-36 hours). Then prime with shellac based BIN.

I know from experience Nature's Miracle works on dog leaving smells. From using it on customer homes and from using 2+ gallons on our present home(previous owner had 5 dogs and carpets) before installing hardwood flooring and removing basement carpet to leave the concrete exposed(my wood shop).

I've read accounts of NM failing on cat urine, but never had a problem so far.

I know they make a cat specific Nature’s Miracle in a spray bottle, perhaps it comes in larger size containers as well.

The best time saver is to use a dual depth moisture meter. Measure at 1/4" depth and then 3/4" depth. If, the reading is equal at both depths. It is saturated through and should be replaced.

If, moisture reading is high at 1/4" depth, then an enzyme can be applied to remove smell. It is time consuming and will require several applications. It can take up to a week to complete.

"We haven’t had cats in 8 years"

G&S, would not think it would still be wet.

If, there is still an odor. Underlying moisture would still be present.

I had an old cat who absolutely saturated my basement laundry room floor with pee. This was a cement floor covered in old tile. We tore up the tile and then put Kilz on it, then painted it. It did get rid of the smell, but this was cement, not wood of course.

Good luck! Cat pee is the worst.