Cat Urinating Outside Litter Box

You guys are going to think I'm a big meanie, but I've got a problem with my
1.5 year-old cat and if it doesn't stop I will have to remove him from my
home.

Three weeks ago I had my roof repaired. The banging was loud and
reverberated throughout the house. My male tabby cat went totally schizo.
It took forever for me to find him, scared as could be hiding in the
furthest corner of the house. I tried everything to soothe him. He
remained scared for several days after the contractors left and he quit
using his litter box.

I have tried to retrain him, and oddly enough he will defacate in the litter
box 80% of the time, but 100% of the time he urinates on the carpet. He
doesn't care where. He still hides in corners and under beds on occasion
and I pick him up and pet him and he is OK for a while.

The roofing thing totally screwed him up. If I had known it would scare him
so much I would have made arrangements to keep him somewhere else. But that
opportunity is gone. Is there any way to retrain a cat to use a litter box,
or am I stuck? I now clean the litter box daily to ensure that the box
itself is not an issue.

Any help is greatly appreciated. I hate to have to get rid of this little
guy, but I can't have him doing this to my home.

G