What do you do when cat uses the new house as a litter box?
really stupid cat
In a new environment, the cat may be freaked out. Confine the kitty to a smaller area initially--don't give it the run of the house.
the cat not stupid.. obviously u r ! cats are supposed to b potty trained as well as dogs
Get a new cat
Get rid of the cat.
Sounds like your cat is "marking" it's new territory-boys are worse than girls. Is your cat neutered? That will help. Make sure the litter box is clean and in a convient place.