I am hanging a TV in a narrow wall space that has no studs behind it. I have verified there are no studs behind the drywall by using two different stud finders (a cheaper and a more expensive model). Both devices did go off once, but only in a small area in the middle of the wall, not along the whole height, so it's definitely not a stud.
This TV mount requires 4 screws. The original plan was to use 4 toggle bolts (a.k.a. drywall screws). However, after pre-drilling the holes, I found that there is another hard surface that begins about 1.5 inches after the drywall. There is no room for the "butterfly" part of the toggle bolt to open up. I don't know what the hard surface is. When I give it a knock with a screwdriver, it sounds like either metal or brick. This is an apartment building over 100 years old. There is another person's apartment behind the wall. A few questions:
1) Should I do additional testing to find out if that surface is brick or metal? If so, how?
2) If not, should I assume it's brick and proceed with trying to put the screws into the brick, either directly or with anchors? What kind of additional gear would this require? Special screws, drill bits, anchors?
3) Alternatively, should I stick with the toggle bolt method, which would require drilling large openings in the second surface to allow for sufficient clearance for the toggle bolts to open? Not sure how easy this would be.