Just to give you some help here, if they are not peeing whilst you are around then they understand they are not to pee in the house. The area where they pee now will smell of wee and they will think it is ok to keep on peeing in the same spot (do not use ammonia or bleach to clean as this has the same smells as urine) You should only tell them off if you catch them in the act. So I would invest some time in that room with them and await the pee! Once they pee, tell the dog off sternly, place it outside and leave for 10 minutes. Allow the dog back in. Every time the dog pees outside - give it the best praise you can. It is back to basics and will take time but whatever you do - dont tell them off when you find a pee withiut catching them in the act as they wont put 2 & 2 together so will just think you come home and tell them off for being there.
Good Luck