urination outside the litterbox

I have a 9.5 year old male cat. Three years ago, we moved into a newy
built house. We were the first residents in the house. Soon, he
started urinating in the corner of the dining room (there has never
been any furniture in that room, it is quite empty). I took him to the
doctor to rule out any medical issues. I used Nature's Miracle, but
to no avail because he would keep urinating in the room. Soon, the
urination spread along the two adjoining walls of the room. There
seemed to be nothing I could do to stop it, I even tried other
products to remove the odor. Since I was not using the room, after
awhile I gave up. I did not notice whether or not he continued to
urinate in that room.

Recently my boyfriend and his 3 year old male cat moved in. We
followed proper introduction procedures for the cats, and they get
along well. They share 2 litterboxes. We wanted to move in his
dining room furniture, but he smelled the cat urine in the dining room
and suggested we take care of that issue first. I hadn't seen my cat
urinate in the room for quite some time (doesn't mean he had stopped),
but the smell wasn't as strong as it had been at one time so I assumed
it was older urine causing the smell. We tried professional carpet
cleaning with special enzymes for pet odors. That didn't work, so I
had the carpet and padding replaced in that room and the adjoining
living room to preserve the same carpet color in both rooms. I
scrubbed the floors underneath the old pad with nature's miracle and
let it sit for a few minutes prior to the new carpet being laid down/
Anyway, that was on Monday. One of the cats (I assume it's mine) has
started urinating in the original corner on the new carpet. I am at
my wit's end and don't know what to do. How can I get him to stop
urinating in that room?? Please help.



CG