My cats will do this if i leave carrier bags lying around on the floor, i dont know what it is but one of them pees on bags. Same with the bathroom, i i use to just leave the door open, now it has to always be closed otherwise there is a nice pile off turd sitting in the bath tub, besides not being very nice in what you wash yourself in, its embarassing if a guest uses your bathroom!
Try to keep the floors free of clothes, bags everything they pee on, and as others said use a good enzyme cleaner, ive found simple solution for cat spray/urine/sick etc etc, and it has a lively smell to it!
What ever you use to clean tho, make sure it soaks right into the carpets etc etc, just cleaning the top of the carpet off wont work, leave it to soak for a good while.