Two Step Training
Washington State University, College of Veterinary Medicine suggests a two-step program for retraining a cat that is urinating inappropriately. It's a pretty simple concept: make his litterbox more attractive to him while making his current spot as unattractive as possible.
Make His Litter Box IrresistibleFirst, give him a new litterbox with clean litter. Cats usually prefer a fine-grained litter, and are not particularly fond of scented litter. Once you've found the brand of litter your cat prefers, don't change brands. (Save your coupon-shopping for products less critical.) Pour about two to three inches of litter into the box--more is not only wasteful, but ineffective.
Put the litter box in a quiet place--cats are very private about their elimination and don't care to be observed. Make sure it's not next to noisy appliances, as that will distract and disturb him. There are a number of new litter box products on the market that feature privacy in one way or another. Just be sure the box is placed in an area where other cats can't sneak up and intimidate the cat who is using it.
If the box sits on a hard, cold surface, you should consider putting a carpet remnant or washable rug under it, as cats like to scratch around the box. It should be in an easily-accessible location. Young kittens and senior cats may not be able to climb stairs easily.
Multi-cat households should ideally have one litter box per cat plus one extra. (We have five boxes for four cats.) Most important: scoop the solid particles out at least daily, and change the litter completely every week or two, washing the pan thoroughly with plain detergent and water or a mild bleach solution (rinse well).
Make The Inappropriate Area UnattractiveNext, you need to remove every bit of evidence of his urine from the place he's been using. There are a number of cleaning products marketed for this purpose, but you can start with plain dishsoap and water on a hard-surface floor, and a regular carpet cleaning solution on carpets, provided the urine is fresh. Caution: don't use a cleaning product containing ammonia. The cat will smell it as urine and attempt to cover it with his own scent by peeing again. Plain soda or seltzer water can be effective in neutralizing fresh urine odor, but for badly soiled carpeting , you'll need an enzyme-based product. There are a number of products on the market for removing the scent of urine. I've reviewed what I consider to be the best in my Top Urine Odor Eliminators article. For more information on removing the odor and stain of urine, also read Cleaning Kitty Accidents.
You can finish by temporarily putting aluminum foil over the area where the cat has peed. Cats don't like the noise and feel of aluminum foil, and as long as they have a new, clean litter box, the switch should be successful.
Once you've set your plan into action, watch your cat and praise him every time he uses his box. This retraining can take time, but with dedication and patience, you and your cat can once again live in peace.