Wall fixing advice

[David Heath]

Hi,

I'd like to put up a monitor arm in my home office. I'm hoping to attach it to the external wall.



I drilled a small hole to test the material in the wall and was surprised that the drill went had some resistance at first, then suddenly moved freely a little way (maybe an inch) and then met resistance again. I stopped at that point unsure that I understood what material I'm drilling into and whether the wall would be able to support the monitor arm weight.

Having done some research, I think this wall is probably a 'dot and dab' construction and therefore I assume there's a plasterboard, with an air gap, and then the main masonry wall. When I tap on the wall with my knuckles it sounds hollow in the area where I drilled, and more solid lower down. The house was built around 1890.

The arm I'm fitting is this one:

https://www.amazon.co.uk/gp/product/B07QTTNTFX/

and it would be to support a 27" monitor weighing 5kg

The arm itself is supplied with two 10mm dia wall plugs and two fairly hefty bolts 8.5cm long (which would penetrate the wall around 7.5cm)



Can anyone advise me about how to best proceed with this. Would the bolts likely be strong enough anyway because they will grip into the underlying masonry because they are long (and quite strong -- 6mm diameter)? Or should I rethink?

This website seems to suggest that you need to cut through the plasterboard and fit a wooden spacer, which is perhaps more than my DIY skills are up to

https://www.diydata.com/general_building/wall_fixings/wall_fixings.php

Thanks in advance for your advice!

David

 

[rsgaz]

10mm dia wall plugs and two fairly hefty bolts 8.5cm long

How long are the plugs? Just get longer coach screws and use the plugs you have.

Start with the length of the plastic plug, add on the extra distance from the face of the block/brick wall to the real face of the wall, and add the thickness of the bracket, which I think you are implying is 10mm.

When you put the plugs in, push them through so they are in the brick/block wall. And DON'T OVERTIGHTEN!!! You'll crush the plasterboard toward into the gap, do it up with a ratchet, not a drill or impact driver and stop when it just clenches up and won't move any more.

 

[David Heath]

How long are the plugs? Just get longer coach screws and use the plugs you have.

the plugs are around 5cm long. Bolts are 8.5cm long. Perhaps that's long enough as-is.. provided that the plugs are properly inserted into the underlying masonry?

When you put the plugs in, push them through so they are in the brick/block wall

ok I see.. push them through the plasterboard flush with the underlying masonry?

And DON'T OVERTIGHTEN!!! You'll crush the plasterboard toward into the gap, do it up with a ratchet, not a drill or impact driver and stop when it just clenches up and won't move any more.

got it!

 

[rsgaz]

provided that the plugs are properly inserted into the underlying masonry?

Yep!

push them through the plasterboard flush with the underlying masonry?

Yep!

 

[David Heath]

Brilliant, thank you @rsgaz!