Inventive advice needed

[exlibris]

One of my cats is peeing on the stairs
I've tried all sorts of things, but essentially he's old and our local unneutered tom is causing his distress, and consequently causing his unpleasant activities.
My concern is that the stuff is getting soaked into the carpet and we don't notice until we've walked thought it - yuk. I need a way to spot when he's done it, or waterproof the carpet, or something! Has anyone else had this problem and could offer some creative suggestions?
Part of me is thinking to remove the carpet, but I don't know what to put in it's place to make the steps safe for us to walk on and to stop him damaging the bare wood.

[Crewella]

A UV torch will show up urine patches. I'll put my thinking cap on.

[meriad]

Firstly, could you catch said tom and have him neutered? Who does he belong to?

Do you have litter boxes in your house so your cat has somewhere to go where he feels safe and not threatened? If you do lift the carpet then what you could do is use a marine varnish to go over the stairs and protect the wood (will take a bit of time to dry though so you may have to do them every alternate step and keep cat off, and then use stair treads at the base to make them anti slip. You can get stick on ones

But definitely invest in at least two litter trays for your cat if you haven't already got, one upstairs and one downstairs and then do that Tom a favour and nab him and get him to a vet

good luck