This wall is not shared by another tenant directly next door but does have a unit above me. I cannot find a stud. i have used a magnet stud finder. I have nailed a 2.5" nail into the wall in 1 inch increments. AND even though the rest of the house is sheetrock, and i saw studs when we were remodeling, i cannot find anything on this wall. the other side of the wall is exterior and perhaps there is a large space between the wall. What can i do??? I have so many holes in the wall now and i cannot place the mirror anywhere else. is there something that is very strong that would work if the mirror were to start falling over. I live in an earthquake zone and i do not feel comfortable having a piece of furniture just leaning against the wall unsecured. super frustrated. Please help.
My preferred anchors in drywall for heavier loads are the newer toggle strap types.
These have a steel brace that rests inside the wall, spreading te load over about 3 inches. They also have the benefit of allowing you to remove and reinstall the bolt, which older toggles didn't allow.
The toggle is installed through a hole, usually 3/8 or 1/2 inch. The straps are slid to rotate the toggle bar until it is perpendicular to the wall. the Toggle is insterted and the straps are then slid back turning the bar parallel to the back of the drywall. The straps are pulled forward and the collar is pushed in to the face of the drywall, locking hte toggle in place. The excess straps are then broken off, and the toggle is ready for a bolt. (It reads loger than it takes.)
You can drill holes in the mirror frame and into the wall to mark where the toggle should go. Once the toggle is installed, you can bolt throught those holes to lock the mirror to the wall. If the mirror is resting on the floor, only two toggles should be needed near the top.
You also could attach the mirror to the toggles using heavy duty braided picture wire. Insert two heavy hookeyes into the back of the frame. You can make an attachment point for the wire at the toggle bolt using a piece of perforated metal strapping, or an S hook bent to close the loops. Put the bolt through this attachment point and into the toggle. Tighten. Then loop the wire through the wall attachment point and the hookeys and close the loop with several twists of wire.
This second method is not meant to hold the mirror tight to the wall, just to provide a leash if it were to tip forward. Again, two toggles should be sufficient.
The weight is not the issue here, since it is resting on the floor. One method could be to use a few corkscrew type drywall anchors on the top and sides of the mirror with metal mirror mounting clips. You can get the anchors and clips at any hardware dept.