How to prepare plasterboard/insulated wall for radiator

[JP_]

OK, so I am soon to internally insulate and plasterboard another room, but this time I want to put a radiator on the wall. Will be using Evergrip pink foam to stick 50mm Kingspan to brick wall, then stick plasterboard to that.

What is the best way to do secure the radiator? Should I just screw on the wall a couple of blocks of wood instead of insulation where the radiator will hang? If so, how much? One long piece at the correct height, or a couple of 100m squares at exactly the right spot? Or is there a better method? Will obviously have cold spots, but will be better than big holes when if falls off .... Will cover in insulation tape to restrict moisture transfer as much as possible.

The wall:

 

[Ian H]

I’d use a couple of 120mm concrete screws with washers through the radiator brackets and into the brick.

 

[endecotp]

How big are the radiators?
I’d agree with Ian for smaller ones.

 

[JP_]

Not sure yet! Rad will be less than 120cm (that's the width of the window).

 

[tomfe]

Bit of copper pipe pushed into the wall where your screws will be.
You can get proprietary fixings like this to minimise cold bridging but they are of course a lot more expensive.

 

[bsr]

I use brown Gripit fixings into the plasterboard and they have worked well. I can hang from the rad without any issues.

You will need to buy their undercutting tool.

 

[^woody^]

Fix battens the thickness of the insulation where the brackets will be. Don't bother with any other concoction, while you have the opportunity to do it right with battens.

BTW, is your method of sticking insulation with foam and then plasterboard to it with foam approved by the manufacturer? Mechanical fixing and interstitial condensation in the inevitable small voids comes to mind.

 

[JP_]

Cheers Woody.

Not sure about that second part ... I am sealing all joints with insulation tape to try to avoid any moisture getting past the insulation. Also, as there is no wooden battens used (apart from rad fittings!) then I guess not such a big problem. At the moment we get a lot of condensation and mould on the inside of the wall, so moving it is preferable at least!

When fitting the battens I'll probably go belt a bracers and cover them in insulation tape, then tape the edges against the boards. It'll be OK!

 

[JP_]

Although, what I could do is put 75mm insulation over the whole wall, then 25mm where the battens go, all sealed up, then put in battens, plasterboard. That'll be solid and reduce cold spots...

 

[^woody^]

You need to be sure that using foam adhesive is actually going to hold the insulation to the wall and the board to the insulation without the foil detaching. Especially as the adhesive will be in patches and not continuous. Normally you would batten the wall insulate between these and then across the face, and then screw the plasterboard on.

For interstitial condensation, the issue will be between the plasterboard and the insulation, and not necessarily between the insulation and wall. Moisture will be stopped by the foil behind the plasterboard and this can then trickle down the foil and come out at floor level. It's very common. It is not an issue when plasterboard is fully adhered to the insulation like with insulated plasterboard, but it can become an issue when you try and make this up yourself and leave air gaps between the two.

 

[JP_]

I see. When I use adhesive I always start with a continuous border that goes right to the edge, then put loads in the middle and once pushed, pretty much the whole lot is covered.
Never thought about foil coming away ... has been OK so far!
Maybe I will pop in some mechanical fixings, just in case.

 

[oldbutnotdead]

I like the copper tube/washer/concrete screws idea.... another similar option is 10mm or 12mm studding and resin
EDIT By the way, when you mention insulation tape on the insulation/battens you are using the foil stuff (not PVC insulation tape) aren't you?

 

[John D v2.0]

You would need some kind of mechanical fixing just to be sure the board is not going to drop off surely. Especially if there's a fire.