We have 2 cats of a year old. They were trained using a litter tray. We took the tray away when they were allowed outside, and have fitted a cat flap which they both use happily. However one of them has started weeing in the house. She started by doing it in the bath, but we noticed she's been using the board the DS'S use for their model railway. She also wees on magazines left on the floor.
It's relatively new behaviour, but I want to nip it in the bud before it becomes a habit.
Any ideas of how to stop it?
TIA