He's not building anything; that's the point of the song. Tom Waits is singing from the point of view of a representative of the paranoid townspeople who view this man with suspicion simply because he seems to be up to something. There is of course no proof for anything he might be up to as it's all in the heads of those around him, and the narration reveals the obsessive and invasive mindset of the suspicious townspeople rather than concentrating on the man who is supposedly building something.
He's not building anything; that's the point of the song. Tom Waits is singing from the point of view of a representative of the paranoid townspeople who view this man with suspicion simply because he seems to be up to something. There is of course no proof for anything he might be up to as it's all in the heads of those around him, and the narration reveals the obsessive and invasive mindset of the suspicious townspeople rather than concentrating on the man who is supposedly building something.