similar problems couple of weeks ago. They started hammering at 1am. I went out and asked the workers to stop and to call their foreman. I was seconded by the security guy of my building. I just show him the telephone and informed that I will call the police if continue... After ten minutes they stopped and since then it never happened. Maybe I was lucky...
I am still by 5am noise, but it is covered by the mosque nearby.. :)