He's living in a house. With walls and doors and, whilst he's not exactly paying the mortgage, it rather reminds him of a conversation he had with Rose underneath a black hole. He pushes the memory away whenever he thinks of it because of the terror and fear the incident had caused, the Beast in the pit who had warned Rose she would die.
Sometimes when she looks at him, he knows she is remembering the same incident.
He's not lived in a house since he and Martha got trapped in the nineteen hundreds, himself a human - as he is now. In fact that entire incident is rather similar in that way.
He is living in a house.
He was windows and walls and doors.
It is almost unbearable. Until he comes into the house one day, after wandering in the garden, and finds Rose painting his bedroom door TARDIS blue.