Walls – Why can’t I find a stud in this wall

The studs will likely be at 16" intervals from a corner, but that corner could be the corner of the building and not the room if you have a wall T'd with another wall. The first 16" could also be more like 15" depending on how the walls are laid out. There are several places you can check to give you more hints:

• The first, and easiest is any outlets and switches. They should be attached to a stud in new construction.
• The next is any trim around the floor or molding around the ceiling, which should be nailed at the studs. You may be able to see small bumps from any nail filler on these.
• And the last method I can think of is to use a light at a sharp angle to see if you can notice bulges in the drywall at 8' intervals. Those are the non-beveled edges at the end of the drywall, and you should be able to notice them if the drywall was installed horizontally (frequently done, but not always).

Beyond those non-destructive options, and the stud finder that you've tried using, you're left with drilling test holes. I'd suggest making the holes close to the floor where they will be less obvious, but not so close that you're hitting the base plate of the wall (you need to be about 2" up).

As Legion600 suggested, you probably have steel studs as furring strips. You need to be sure you are not hitting protection plates installed on wood studs.

These protect electrical or plumbing lines close to the stud face, and you must never attempt to drill through these. Usually, if you drill several inches above or below such plates, you will hit wood. If you are hitting metal along the entire stud length, it is not a protection plate, but a metal stud. Metal studs in this application should be fairly light gauge and easy to drill through. Protection plates are about 16 GA and are not easy to drill through.

You may anchor objects to metal studs. They are sturdy enough when finish sheathing is attached along their length. Do not use toggles, the hole required is too large. It's best to use a number of self-drilling screws that are barely long enough to engage the stud face material after passing through the mount and wall finish. This avoids damaging any lines routed through the center holes of the stud. You can also use self tapping screws into pre-drilled holes, but drill very carefully so as not to damage any underlying lines when the drill breaks through the face material, and again, use appropriate length screws.