Our cat does this too Lyn, I was given all kinds of reasons or excuses for this behaviour. I was told she was marking her territory, possibly didn't like her kitty litter,(we were using clumping at the time), or her box needed changing more often. She has slowed down a bit, but we are still occasionally surprised to put on a soaked shoe left on the boot tray inside the door. We have started picking up everything laying around on the floor. Also my husband has tried putting cayenne pepper on her favourite spots, this also seems to help. We were also told that if you have two cats, to make sure you have two litter boxes. Hope some of these hints help.