Facts of Marking/Spraying

Cats mark their territory by ´spraying´ their urine on objects: car tires, bushes, lawn furniture, house doors, gates, rocks, electrical poles... etc. In some cases, they will use their solid waste as a territorial marker, also.
Cats will continue to mark their territory, as long as they can smell their own urine or any other cat´s urine on an object. It is the same with the solid waste odors, also.
The feline sense of smell is much more sensitive than humans, so simple soap and water will not remove the micororganisms of urine/feces that the cats can smell. To remove that odor you must use an enzymatic cleaner or one of the other formulas found in Litter Box Blues: Odor Removers.