I'm in a new apartment (built 1 year ago) and I am trying to hang a wall mirror (about 50-ish pounds). I've tried 2 different sizes of drywall anchors but the anchors only reach about 1/2inch into the wall before resistance pushes them back out. I'm not on any studs and I can't see anything in the wall that could be causing the issue. It's a shared wall with one of the building's stairwells. The only thing I can think of is there may be some sort of reinforcement behind the drywall for the stairwell. Has anyone encountered this problem before or know how to solve the problem? Maybe a drill could put screws in the wall and hold just as well since the anchors don't seem to be useful in this situation?
You may be hitting a block fire wall. Many types of hangers out there. Do not recommend making holes in firewall.