Fixing radiator to insulated plasterboard wall

kempiejon

I have fixed heavy screens to plasterboard, usually I could find studs or use those "clever" fixings that hang onto the plasterboard using the gaps between studs and board hollow wall anchors and Gripits.
Occasionally I had more exotic plasterboard constructions and I made a good fix using a piece of ply or MDF (drill pilot holes) and grab adhesive. The MDF gives something for the mounting screws to grab and the piece of MDF gave a large area to hold to the plasterboard. I've supported my own 90kg body weight from a TV bracket and 4 screws to test.

ThisIsWeird

Strummer22 said:

I need to install a new radiator on a wall with 62.5 mm insulated plasterboard over cement render skim and thermalite blockwork. The insulated plasterboard is bonded directly to the render with insulated plasterboard fixings too.
The radiator weighs about 32 kg empty.
What's the best method to attach the radiator? I had thought long fixings into the blockwork would work, but having doubts now due to a) cold bridging and b) too much load on a single point.
These also appear to be an option: https://www.amazon.co.uk/Bullfix-Universal-Pack-Plasterboard-Insulated/dp/B092FSQWS7/ as they claim to hold tens of kg, but I just want to make sure that whatever is used won't damage the insulated plasterboard or risk falling off the wall. Any advice gratefully received.

Hi Strummer.

FreeBear's comment is worth considering - does the rad need to be mounted on this external wall? No internal wall alternatives?

Assuming you have no choice, and also assuming that this rad comes with conventional L-shaped metal brackets, then a thing to bear in mind about plasterboard is that it's astonishing strong, provided no-one starts to move things about. Ie, great for static loads, but a bit pants for dynamic. So, will anyone lean against it at regular intervals? Will anyone tie a rope to it and climb out t'window?

No? Cool - so it's almost certainly perfectly good enough to hold even a heavy rad, provided no-one shoogles it about. And the way to prevent shoogling is to... glue it.

I like these:

 

Provided you fit them correctly, then they are incredibly strong. 'Correctly' means to use a correctly-sized drill bit, often a mm or half-mm smaller than recommended, and to drill slowly so's it doesn't 'burst' through the back of the p'board and tear - weaken - the 'board, and then to tighten these up without moving them too much and tearing the paper layers. Once fixed, these are great. P'board's strength lies in its paper layers.

So, accurately mark out where the two(?) brackets go, drill the mounting holes steadily and crisply, push through the drywall fixings, hold them securely whilst you tighten them down, double-check all the measurements (eg, dry-fit the rad and check it's level), and then finally 'glue' the bracket to the bare p'board using something like StixAll, whilst you tighten down the fixings. 

These brackets will now not move. At least not without taking a huge section of p'board with it - which it won't. No cold bridging. Jobbie almost certainly jobbed.

FreeBear

ThisIsWeird said: I like these:

 

Provided you fit them correctly, then they are incredibly strong. 'Correctly' means to use a correctly-sized drill bit, often a mm or half-mm smaller than recommended, and to drill slowly so's it doesn't 'burst' through the back of the p'board and tear - weaken - the 'board, and then to tighten these up without moving them too much and tearing the paper layers. Once fixed, these are great. P'board's strength lies in its paper layers.

Plasterboard is only good for loads up to 15-20Kg/m². Radiator brackets are not going to have sufficient surface area to evenly distribute 32Kg. So the load needs to be transferred to the blockwork behind. Something like the Corefix could work if the steel sleeve were longer and it had decent penetration in to the block.

The fixing you show wouldn't last more than a few minutes.

ThisIsWeird

FreeBear said:

ThisIsWeird said: I like these:

 

Provided you fit them correctly, then they are incredibly strong. 'Correctly' means to use a correctly-sized drill bit, often a mm or half-mm smaller than recommended, and to drill slowly so's it doesn't 'burst' through the back of the p'board and tear - weaken - the 'board, and then to tighten these up without moving them too much and tearing the paper layers. Once fixed, these are great. P'board's strength lies in its paper layers.

Plasterboard is only good for loads up to 15-20Kg/m². Radiator brackets are not going to have sufficient surface area to evenly distribute 32Kg. So the load needs to be transferred to the blockwork behind. Something like the Corefix could work if the steel sleeve were longer and it had decent penetration in to the block.

The fixing you show wouldn't last more than a few minutes.

And yet I weigh around 85kg, and could hang off one of these brackets.

Grenage

But not for years, and you have to consider someone knocking or pushing on the radiator. 

Setting tools are the way to go with those hollow wall anchors.

Murmansk

Use resin fixings - you can hang a car off them!

jonnydeppiwish!

I have these holding up 40kg rads off the same insulated plaster board. The brackets are large enough to disperse the force and there is no movement

https://www.screwfix.com/p/fischer-duopower-wall-plugs-10mm-x-50mm-50-pack/5424p

ThisIsWeird

Seriously, glue the brackets to the p'board as well. It's not to 'stick' them on there - tho' it'll help - but to prevent movement, which is the killer.

You just ain't going to pull a foot-long section of p'board off the wall.

rob7475

Another option if using a "designer" type radiator is to use radiator feet to take the weight. The brackets in the wall are then just supporting the radiator so it doesn't move away from the wall