I am trying to mount a projector to the basement ceiling. I have found a joist where I want to put it but there is a light nearby. I would like to make sure that there are no wires that I might go through. How can I check? I tried using my stud/wire detector but it is unreliable. Also, the joist end has duct work on one side and is capped by metal on the other. Why?

I have an exposed ceiling beam in the living room held up by 3 columns. I want to replace it with a lvl and get rid of the columns. The span is 30ft I consulted an engineer and he specified 3 1-1/2 16" 30ft Lvl beams. My question is. The beam is at what used to be the outside wall of the house, they built a porch and enclosed it, then built another porch outside that. So the beam is about 10ft from what used to be the center of the house and about 10ft from the new outside wall which is mostly windows. Looking inthe attic the house is stick built and rafters run from the old center of the house to the new outside wall 20ft. With the beam at 10ft. On top of the rafters there is for a better word a ladder beam (looks like a ladder on side) sitting on the existing beam and the roof is sitting on top of that. If I build walls on each side of the existing beam and then remove the old beam, everything is ok. However as soon as I cut the rafters to put up the lvl inside the attic, those walls I just built are not holding up anything but the tail ends of the rafters. I cant see that they are really supporting any weight except the ends of the rafters. Also that ladder beam will not be supporting the roof anymore until I get the new beams up and a new ladder wall built on top. I cant see how this can be done without having nothing holding up the ceiling. The only way I can see is to leave the old beam in place, cut the rafters on one side. Raise one lvl beside the old beam and build a new ladder wall on top of it then remove the old beam and put up the other 2 lvls. What do you think?