We have two cats who are allowed outside but only via the door when we let them in or out, no cat flap. We recently moved house and one of the main things we wanted was a cat flap, especially so that we could do away with the litter tray.
However, now we're here we're wondering if the cat flap is such a good idea as they would probably bring dead (or nearly dead) things in and roam the corridors at night disturbing us.
Currently we shut them in the living room and an upstairs room which adjoins it, which is where the litter tray is. This arrangement works quite well, we except for that the litter tray absolutely reeks. No matter how often we change it, they immediately do something foul in it - almost deliberate scent marking. It really spoils our lovely new house.
I can't really think of a solution other than just taking the litter tray away and hoping that they can make it through the night without needing the toilet. Does anyone else have a cat who stays in at night with no litter tray?