Thanks everyone, I appreciate all replies and opinions. I didn't know exactly where the pipes were, only that they were somewhere in the wall, and must be close to the radiator. Most people would not know where their pipes were, does this excuse the carpenter? I didn't run the pipes, but I honestly don't see an alternative here? There is a solid floor so can't put the pipes there. Surely they wouldn't be run across the middle of the wall, where no-one would ever expect them. It doesn't seem too unreasonable to me to put them in line with the radiator outlets. They were buried quite deep, only 2" nails or longer would hit them. It's not true to say that I knew pipes were hidden. I knew pipes were in the wall but only because they couldn't have been in the floor. To anyone who looked at the room, they couldn't have been anywhere else. Things are often in the wrong place, that doesn't mean you should deny the possibility. An amount of due diligence is surely expected, is it not normal to use a pipe finder if you're about to shoot nails into a wall?