We have brought an old house where the infirm old man who owned it was not very good at aiming therefore he urinated on the floor around the toilet. How can we remove the smell? Will we have to replace floor boards?

If cleaning won't remove the smell, you may need to rip out the existing flooring and replace it. What is the existing floor finish? Hopefully the urine did not make it to the floor boards.

Al in Florida just explained to me how an Ozonator shock treatment machine can work wonders with odors like this. You can hire some one or rent a machine on your own. What is your flooring material, hope its not carpet.

Like Ballengerb1 said, rent an ozone generator. It should knock the smell out. Rent one that has at least 2 grams/ hour. It will kill the odor without harming everything like chemicals would.

If you can't find one locally, ozonesupplies.com rents them. If you wanted to purchase one, I could help you. But, I'm not set up to rent except locally.

It is amazing the way it removes odors. Type in ozone on the search on this page. You'll see some of my other posts about it.
Al