Mount TV on insulated plasterboard and cavity block

The_B_Man

Hi, I want to mount a 65" flat screen on the wall. It weighs 14.3kg.

The wall where I had the electrician put in the power and HDMI ports is on a cavity block wall (not a cavity wall). The wires aren't in any kind of run behind the plasterboard (they're just loose hanging, as far as I remember, so nothing else to hang onto).

The wall has insulation on the inside. Not sure the thickness of the insulated plasterboard.

The concern was raised that I can't screw in the mount because there's not enough brick to grab onto in the cavity block unless i'm lucky to find the non-cavity parts. Also, the insulation on top of it won't hold the TV because it's foam and just not strong enough.

I spoke to a few people and got conflicting advice.

1. I can screw in the wall mount no bother because it has 8 screws and they're rated for 5kg each so it should be grand.
2. I need to cut out a chunk of the insulated plasterboard and hang a bit of wood on the wall, then replace the plaster and then I can safely screw on the wall mount.

I think it's a bit much to be ripping out insulation back to the brick just to hang a TV but I'm not opposed to it if I have no option. In which case, how can I ensure it's still insulated and I don't get a cold patch in the wall?

Or is the other person correct, and I'll be grand to drill into the cavity block since the TV is less than 15kg and the weight will be spread out across all the screws?

Thanks in advance.

Paul.kavanagh

Can you guage the depth from the front of the plaster finish to the actual cavity block ? what type of bracket are you using ? flat mount or swing arm ?

The_B_Man

It'll be a flat mount, not swing arm. Might have a bit of swivel, that's about it.

For the insulation, I'm not sure the thickness. Don't think it's huge. I have photos from when it was added. See below:

James Bond Junior

https://www.screwfix.ie/p/bullfix-str-uni-10-universal-plasterboard-fixings-24mm-x-44mm-10-pack/172ja

I've used these to hang a 10kg mirror on insulated plaster board. They are brilliant, only used two and it is solid.

ted1

would you not just use a sleeve anchor through the block. No need to cut out insulation just use one long enough that’ll go through it and the wall and then tighten up the bracket.

10-10-20

If you drill the cavity block carefully with the correct 10mm bit (try use light pressure with hammer action) and not blow the rear face of the cavity blocks off, then you might be able to use the corefix products…

https://www.screwfix.ie/p/corefix-connect-120-heavy-duty-dot-dab-wall-fixings-10mm-x-95mm-4-pack/334rg

Paul.kavanagh

Generally, the mounting screw holes on the back of the tv arebetween 200/400 mm in width apart.

Get a flat mount bracket that is 400mm wide and use these guys, each one can hold 15Kg so using 6 of them evenly spaced across a 400mm flat bracket will be more than enough.

https://www.screwfix.ie/p/rawlplug-tap-it-plasterboard-fixings-screws-metal-30mm-25-pack/7610p

The Continental Op

Why would anyone use plasterboard fixings when they can screw into the blockwork?

Paul.kavanagh

It depends on a persons level of diy skills ? do they have a drill ? suitable drill bit lenght, ect , just offering an easy solution that works.

ted1

https://www.boards.ie/discussion/comment/123938209#Comment_123938209

I’ve zero trust in any plasterboard fittings.
Drills aren’t expensive, a good SDS from is less than €50

Paul.kavanagh

https://www.boards.ie/discussion/comment/123938260#Comment_123938260

15kg aint alot in terms of screens these days when the weight is spread over an area of nearly half a meter.

The_B_Man

Ye I'm wary of relying on the plasterboard alone. This TV is light but what if it breaks and I replace it with a heavier one. Don't wanna be stuck.

I was actually looking at screws like these:

https://www.screwfix.ie/p/easydrive-tx-countersunk-thread-forming-concrete-screws-7-5mm-x-100mm-100-pack/3839h

Although I like the ones using the sleeve.

I'm not gonna do it myself. I'll get a tradey friend to do it and throw him a few euro for his trouble. My DIY skills wouldn't be up to the tasks. Or they might, but don't wanna risk it. Would rather it be done right.

The Continental Op

The ones with the sleeves help stop the weight sagging downwards. The screws in the sets will be easier to remove in the future than the thread forming screws. Also the thread forming screws won't be quite as kind on the blockwork and would have more chance of damaging it than the plugs on the other sleeved set.

sundodger5

I didn't do a tv but it was 4 ikea Kallax shelf units into similar insulated board.

I used something similar to these. https://www.screwfix.ie/p/easyfix-hollow-wall-anchors-8-16mm-m5-x-52mm-10-pack/12229?gclsrc=aw.ds&gad_source=1&gad_campaignid=19671793576&gclid=CjwKCAjwjffHBhBuEiwAKMb8pNcnD_DZU-l4FqYTELF2ME65BS_SZarvRNl3xIAT_hioq1REV8OuVRoC7GkQAvD_BwE

Trick was stopping the whole thing rotating until they took a bite at the back of the board.

pugleon

https://www.boards.ie/discussion/comment/123936301#Comment_123936301

Corefix worked well on my mount can second that notion

niallb

I'll add a third recommendation for corefix. I used them to mount a shelf and clothes rail on a wall in my son's room 7 or 8 years ago and it hasn't budged no matter what (or who!) was hung out of it.

Idbatterim

Just put the plugs into the masonry, drill in. Screw the screw into the raw plug a little bit. Tap it into the hole with hammer... take out screws, fit the bracket, screw into rawplugs... getting tvs mounted isn't expensive. Loads of companies in Dublin do it, if you don't feel comfortable, tackling it yourself...

Idbatterim

You can't use hollow walls anchors on insulated board. They can't open and expand...

The_B_Man

I like the look of those Corefix ones. Reading the description it says:

"10-30mm maximum fixture depth. 45mm maximum distance to blockwork from face of plasterboard"

So how does this work now with my insulated plasterboard? From the image, it seems to work for plasterboard directly on the brick. I'd probably end up with the steel core just hanging in the insulation and nowhere near the brick.

niallb

I had an uneven gap between the plaster board and the blocks.
Corefix come in different lengths, like 100mm or 120mm, but the main difference is in the shank, so it can accomodate something thicker on the surface - compare mounting your steel plate as against a drilled wooden batten.
From the surface of the plasterboard, there's a maximum distance to the block so that there's enough depth to hold the collar.

basillarkin

concrete screws into the blockwork