Best way to eliminate old urine markings?

I spent the holiday weekend doing some spring cleaning in the basement, and oh boy what a disaster awaited me!! For weeks I kept cleaning the boxes and keeping the rest of the rooms in our semi-finished basement spotless yet I could not understand why it still smelled like pee! Well, turned out someone decided that under the stairs was a suitable place for that and who knows how long it was going on. I soaked the entire floor in that room with hot water and bleach, then again with a regular cleaner. Any tips for gettin this stuff out of the floors for good? There is vinyl tile and cement under it, and I fear that I may have to rip out the tile under the stairs. UGH cats!!! Merlin watched me as I hauled out all of the junk and mopped up his mess (well, it wasn't just him but I know what he gets up to sometimes!) If it wasn't for those fluffy faces, bushy tails, and chirpy greetings I'd just give up!

I was wondering the same thing. We have old wood floors with cracks between the boards and I really don't want to pull those up. Baking soda is my first plan of attack, if that doesn't work I don't have any other good ideas.

I don't know about urine but I once dropped a glass of red wine on a beige carpet - as you imagine, whatever I tried just made it worse, but I decided to try some mouthwash (Colgate Max White One) - just pour a little bit - doesn't work on the teeth, but very efficient on carpets, you can't see the stain any more - and it's minty fresh!
Where Trespasser (Neevie's friend who comes to say hi) peed repeatedly on the doorstep, I washed with water and whatever detergent I had at hand, but Trespasser came back and did it again ... untill I took half a lemon, and just scrubbed the whole surface (which I had just washed) directly with the lemon. Trespasser never peed there again. Obviously can't really do that with carpet, but may be once you have tried the mouthwash, try to spray with lemon juice so they hopefully don't feel like going there again?

The floor is vinyl tile over cement. After I bleached the floor I washed it again with a special enzyme cleaner called Natures Miracle. It does a fantastic job gettin the smell out. After that I spray with Feliway, but at $32 a bottle Id rather try the lemon!!!
Merlin has another urinary tract infection, looking at chronic feline cystitis so I'm pretty used to cleaning pee, although usually fresh pee. He was not pleased that I cleaned his "spot" and is now peeing in a new spot...We're off to the vet tomorrow for more antibiotics, and hopefully a respite from his accidents. I dropped off a urine sample yesterday and expected them to just order meds as usual, but they asked me to bring him in for an exam. I hope there isn't anything else going on that they wouldn't tell me over the phone :-/

There is a recipe which I have used with some success, a mixture of biological wash liquid, vinegar and warm water. Sprinkle it on to the affected area, as much as you think is needed, then leave to dry. Once dry, rub in some bicarbonate of soda, leave for an hour, then vacuum the area. I found the recipe online.

I will definitely try both the lemon and the baking soda! The spot under the stairs still has a faint pee smell and even the enzyme cleaner isn't getting all of it.
We too have a visiting stray. I call him Banshee because he screams like one when he's causing trouble with Sampson and Merlin. He's been around since the winter but only recently has he been frequenting us on a daily basis. I've wondered if his presence has been upsetting Merlin, but it's hard to tell!
At the suggestion of our vet I moved a litter box to Merlin's pee area in the basement. He did turn out to have a mild urinary infection too and is on another round of antibiotics. However, once I moved the litter box voila! No more messes!!! I don't know if it's the box, the medicine, or Merlin finally giving Banshee a piece of his mind and being allowed to mark his territory outside but *for now* the accidents have stopped. Our local shelter has spay-a-stray programs for $5, and we are going to take Banshee in. This will not only help with the turf wars but also prevent more unwanted kittens. At last count the feral colony in our neighborhood stood at 60 cats, and that's a loose estimate. :-O

waw! 60 unspayed cats roaming around.... breeding like rabbits.... that's Alekto heaven! (though husband would probably protest at the £ spent to feed them...)

It is a terrible problem with no solutions. The neighborhood association tried a trapping campaign a few years ago but that failed, as euthanasia alone will not lower the numbers (nevermind that it is cruel and wrong). One woman on the street behind ours has taken in several and had them spayed and neutered, but then other neighbors get angry when they find kitty poo in their gardens or paw prints on their cars. Still others try to say that outside cats kill songbirds and other animals, but we feed birds and have a regular stream of finches, woodpeckers, jays, wrens, and all kinds of birds so that isn't true. And what if the neighborhood did eliminate all stray cats? It would be a matter of time before mice and rats take over, then they would be complaining about that! Our house is next to a hair salon and the owner loves our cats because they do hunt mice and keep them from coming into her business.