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hstraf 09-05-2011 03:43 AM

TV wall mount in drywall/foam/block combo with no studs?

I need some help to determine the best solution for mounting a large TV to my house wall.

The TV weighs about 44 lbs (20kg) and has a 42" screen.

The holder that nees to attach to the wall looks like this:

So... the problem is that the building is made out of cement block. The drywall is attached to the blocks using glue... and there's about a 3" piece of gray (insulation) styrofoam between the block and the drywall.

So it is like this:

Standard cement block, then 3" gray styrofoam insulation (glued to the block), then 1/2" drywall glued to the styrofoam.

(This is very odd for North America, but is very common where the house is located in France where I am living.)

Does anyone know what is the best (safest, as I have three small children who will eventually want to hang from the TV, because hey.. isn't that fun!?) way to put this on my wall?

I thought maybe I can find some heavy-duty fly anchors that go into the drywall (each bolt says it can handle 40 lbs), but then I thought... the drywall is basically just glued to the foam, which is glued to the block.. so there would be a lot of "wiggle" after some time.

Then I thought... maybe I can put a long bold right through the drywall into the block... but that would be at least a 4" bold and would also result in a lot of "wiggle" especially if I tighten the bolt too much.

Then.. I thought I could cut out a section of drywall and foam that is exactly the size of the wall mount unit, and attach the unit directly to the block. This would be pretty solid... but I'm not sure cement blocks are designed to do have things attached to them like that? (What kind of bolt should I use?) This method would also be rather ugly, as it means there's a big hole in the wall.

Any suggestions?


Ron6519 09-05-2011 07:40 AM

Open the wall and install wood blocking to the concrete so you can bolt the mount securely to the wall.

rjniles 09-05-2011 07:48 AM

Do you really need that articulated arm mount? They put tremendous stress on the mounting bolts and tempt kids to hang on. A flat to the wall mount could be bolted thru to the block with masonry anchors.

If you must, cut out the drywall and foam, attach wood blocking. to the masonry and reinstall the drywall.

hstraf 09-06-2011 01:51 AM


Unfortunately, I have no choice to use an articulating mount. The wall where the TV will hang is at an odd angle to the viewing area, and the only solution is to move the wall or hang the TV on an "angle" from the wall. It will rarely be fully extended, though... (And I might put a cow fence on the bottom of the TV to keep the kids off. haha.)

Ok.. so it looks like cutting through the drywall/foam and mounting a piece of wood directly to the block is the best solution. Then I will attach the TV mount to the wood.

This works out ok, (although it's ugly), since I would like to run the wires behind the wall and having the cutout will make it a lot easier...

So.. of course my next question is.. what is the best type of bolt/screw for mounting the wood to the block? Unfortunately, I won't know in advance if the bolt will be in the "hollow" of the brick, through the mortar, etc..

Any suggestions for the best most secure attachement of the wood to the cement blocks?

Thanks again!

rjniles 09-06-2011 04:41 AM

If you are in the core use heavy duty toggle bolts, in the mortar use lead shields and lag bolts. Also use construction adhesive.

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