What's this metal thing in my wall where the studs should be, and how do I put a shelf on it?

Question

I'm attempting to mount a shelving system (specifically, a Rubbermaid single-track adjustable shelf) to a wall and am running into something quite strange.

Here's what I know:

• Studfinder appears to show studs at 16" intervals.
• Upon drilling a pilot hole on one of these intervals, the bit pops right through the 1/2" drywall, passes without resistance through a small bit of free space, then runs into something hard to drill through.
• Removing the bit from the drill and manually poking the offending substance produces an airy sound, like a big metal plate.
• Drilling a few feet upward at the same horizontal position yields the same result.

The wall is an interior wall in a recently-built high-rise apartment building shared between two apartments.

My questions:

• What's this metal thing I'm hitting? (I doubt it's a protective plate, as it spans the height of the wall, and sources say a metal stud should be "easy to drill through", which this is not.)
• Why am I (apparently) finding a gap behind the drywall and no stud at these 16" intervals?
• What are my options for mounting this shelf now? (Toggle bolts?)

Further testing I plan to try:

• Scanning wall with a strong magnet (my hard drive magnet hasn't shown me anything yet...)
• ...yeah, I'm out of ideas.

Thanks in advance!

Answer 1

Given that this wall separates two apartments in recent construction, the wall you're drilling is likely not to be "normal" familiar construction. It's probably some kind of "area separation wall" designed firstly to limit the spread of fire and secondly to limit the spread of noise between apartments. You might do well to seek information from building management as to the construction of that wall to ensure that you don't compromise its fire resistance characteristics.

Answer 2

The first few times I found metal top hat or metal supports in the ceiling I think I drilled 4 or 5 holes before asking my dad.

he looked at the floor and had a screwdriver that was magnetic, he passed it through the dust and there was a bunch of metal, I did not notice at first.

Later when finding metal studs a few times over the years I have found metal studs where doors were in a wood structure the magnet trick pulling up metal has helped me with identifying metal studs, including top hat or metal furring strips and even identification that I have hit rebar in a concrete wall or slab. Any magnet will pull the metal up the more flakes the higher chance that you hit or went through metal.

The last possibility is a nail plate , a steel plate to protect electrical wires that are less than 1-1/4 “ behind the face of a stud. These are thicker than metal studs or the top hat furring strips and usually create a fair amount of metal filings.

I hope this info helps, there are other possibilities less likely that are like water pipes but they are even thicker but a possibility that you skinned one as your stud finder thought it was a solid is a possibility.