Need help mounting a TV to the wall

Question

I'm struggling to mount my 31kg Panasonic TH-P60ST60A 60 inch TV to the wall in my apartment and was hoping someone here might be able to give me some advice.

The walls in my apartment seem to be a layer of drywall, about 20mm thick, followed by a 10mm gap, and then some type of brick. As far as I know, there are no studs in this wall (it's in Australia, and the walls here seem to be constructed quite differently from the walls I'm used to in Canada):

I used a hammer drill to put 8 holes in the wall, when I drilled through the drywall, it was pretty easy, but I had to switch to the hammer when I reached the brick (or whatever it is) behind the drywall, so it seemed somewhat solid, although definitely not as solid as the type of brick you'd find outside:

I then used the following 8mm x 80mm plastic plugs

and tried to push them as far back as possible, to try to get them seated into the brick:

Then I put the TV mount on the wall and tried fastening some large screws into the plastic plugs to secure it to the wall, although unfortunately what ended up happening is that the screw just twisted the plastic plug, and it eventually just broke off:

Here's a picture of the wall with the mounting bracket waiting to be screwed in:

You can see that there's a large gap in the wall, which the owners thought was a great idea, but I beg to differ. I was still able to drill 4 holes with 100mm spacing, which I figured should provide enough support (if I was able to get a solid bolt in the wall, that is)

So now I'm stuck. I have 8 ugly holes in my wall (actually, 9 because I drilled one too close to the corner and hit the metal bracket) and I haven't been able to attach a single screw.

I think there's two main issues so far:

1. I used an 8mm drill bit for an 8mm plug, but the "brick/stone/whatever" behind the wall might have been too soft, in which case I may have made the hole too large, so the plugs are just rotating around not gripping
2. Perhaps I didn't actually push the plug far enough into the wall so that it reached the brick, in which case when I twist the screw, it just shears off the top of the plug because it has nothing to grip on, however, I've pushed the plug pretty far into the wall, and it feels like it's seated in the brick, but I can't really tell for sure.

In any case I'm at a loss of what to do next. I'd like to avoid calling a professional, since they charge about $400 to mount a TV and was hoping I could do it myself, but now I'm stuck. If anyone has any suggestions of what to try next, please let me know! Thanks!

Edit: here are some additional pictures of the gap behind the wall:

And a close up of the screw inside the plastic plug:

And a google sketchup diagram of possibly using a wooden frame to support the TV:

Update May 25th 2017

Thanks to all those who answered, you gave me some great suggestions, and I'm happy to report that I've finally managed to mount the TV on the wall!

I took AndyT's advice and bought some larger 10mm plugs for my 8mm screws. While I was drilling the larger holes, it felt like I hit brick behind the wall, and the screws feel pretty sturdy, as does the bracket, so I think the TV should be secure.

Here's some pics of the bracket and TV now attached to the wall:

Answer 1

If the top of the plug is shearing off when you put the bolt in, then this means the bottom of the plug isn't turning (so not a problem of the hole being too large), but the top of the plug is turning (which means the bolt is gripping it rather than turning within it).

Looking at the picture of your bolt in the partially failed plug, and given the above, I believe your plug diameter is too small for your bolt. Your options would therefore be to either get smaller bolts, or to get larger plugs (and drill a larger hole for them).

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An alternative would be to get a different sort of plug. There is a product called "grip-it" designed to attach to plasterboard (=drywall) which has been installed dot-and-dab over masonry as per your situation. I've found it to work well, but the diameter of the fixing is very large, so is only suitable when the bolt won't be near to a visible edge. The business started in the UK, I have no idea whether it's available in Australia.

Answer 2

This is a challenging situation to support an expensive TV. I simply wouldn't trust anchors in brick of unknown quality and condition, especially with those working conditions and the leverage of a big gap between the anchor and the load.

It isn't clear if your last picture is of the same location. If it is, the opening behind the mount is almost certainly framed with lumber, and you could use lag bolts or heavy screws into those studs. I'll assume, though, that picture is just to illustrate the TV mount.

There are toggles of various designs for drywall that are rated for big loads. You can support almost anything with enough of them. But you have only a small gap behind the drywall, and I would be concerned about there being adequate space for the wings to properly deploy.

I would also be concerned about the structural strength of the drywall. It is normally fastened to periodic studs, even when the drywall is used like paneling, which serve to reinforce it. In this case, it looks like someone just wanted to hide the brick with a decorative sheet of drywall. A 10mm gap might just be something like a strip of plywood top and bottom to leave an air gap between the drywall and the brick.

If it were my TV, I would approach it a different way. I wouldn't rely on that wall to support the TV. I would mount it on something "structural" that is independent. Two approaches:

• If that wall is fairly narrow, where the drywall is wrapping an old brick feature, there will likely be framing in the corners. If so, and assuming actual studs were used, you can fasten a horizontal board to those studs, running the whole width of the wall. Use one at the height of the top of the mount and one at the bottom. You can add a few drywall anchors to hold the boards tight against the wall in the middle and to counteract sagging. Paint the boards to match the wall and fasten the TV mount to the boards.

• If that's not the case, fasten the TV mount to essentially freestanding poles. There are fancy poles designed for this purpose, but you can just use a couple of boards painted to blend in. The floor supports the weight. The boards are fastened to the wall or ceiling joists just to keep them upright and plumb.

  Instead of two independent boards, you can add top and bottom boards to create a rectangular box that fits tightly floor to ceiling. Then a few nails through the horizontal boards into the floor and ceiling will keep it from moving. When you leave, there will just be a few nail holes to fill.