I am redoing the ceiling in my daughters bedroom, and will have access to the entire ceiling. In the process, I would like to place an electrical box for a ceiling fan. There is no attic, and the room is just on the other side of the ceiling. I would have to drill through the room beams/truss to get the electrical wiring and box in place before insulating. Is this permitted? If so, where along the beams/truss am I allowed to drill to pull the new electrical wiring?
There are several different types of structures that fall under you description. First thing if you have a beam or truss you need to check to see if it id structural.
Truss are made up of many small pieces and you can not drill through them without destroying their structural integrity. You will find truss in newer home and normally there is plenty of room to run wire between the individual pieces that make up a truss.
Beams normally refer to a structural member that hold up other smaller members. You may had a beam at the ridge of your house that will hold up your roof rafter. You do not want to drill through beams unless you know that they are designed in such a way that it can take the hole.
I think you have floor joist in the room you are describing. In that case you can drill a hole in the joist. You will want the home as close to center as you can get it. Since the beam is bending down the, top of a beam is under compression and the bottom is under tension. In the center of the beam there is no force so a hole will not damage the structure. You need to be 2 inches from the outside edge as a minimal requirement.