Hi Sascha! When I went to put up my x-pole for the first time, I had a stud finder (an expensive one!) but it still couldn’t really find the stud! I called a friend who owns a contracting company, he’s a carpenter. He told me that ceilings that have a roof over them have many other metals and stuff in them because they are actually called "stringers" not joists, joists are in a ceiling if there is a another floor above that ceiling. Well any way my point is that it’s not always accurate with a stud finder in that situation, and if your ceiling is plaster and not sheet rock, your reading is usually a false reading. He told me to find out which way the stringer runs, then measure from the outside wall (which would be where my window is) over and mark off every 16 inches (in the US) until I find where I wanted to put my pole. That’s how I had to do it. He recommends that’s the way it should be done to prevent damage to the ceiling. Hope this helps hun, cause it probably wasn’t your stud finder!