Corefix screws for radiator brackets are not biting. Suggestions?

[Mattso]

Hello. After plenty of resaerch I decided to go for Corefix 120 screws to attach 8 screws for 4 radiator brackets. The wall is, from inside to outside: 

 

plaster -> plasterboard -> 40mm celotex PIR -> old plaster -> External brick wall. 

 

Made the appropriate holes with the recommended dirll bit of 10mm diameter. When attaching the screws and gently screwing them into the core & plug, some bite. Others just end up spinning while the plug stays in place. So the screw just chews into the plug and when i pull the whole the screw away from the wall, the entire plug and bracket just comes away from the wall. So the plug is not doing what it should. 

 

I had the suspicion that the plug was too short, so I also cut the head of the plug off and pushed the plug & core 30-50mm inside the hole. Was hoping more of the plug would be in the brick. The result was equally unsuccessful.

 

The only other idea I have is to use a smaller drill bit to make a smaller hole in the brick, in order to squeeze the plug and force the screw to bit. 

 

Other than that I have no clue how I will get this radiator installed in the wall.

 

Any suggestions are welcome, short of questioning the use of internal insulation 🙂

 

Below is an image of the schematic of the wall. 

 

Thank you

[Mr Punter]

Charlie DIYte did a decent review of plasterboard fixings.  Insulated plasterboard at about 25 mins in.

 

 

[MikeGrahamT21]

I would say they aren’t long enough, the top layer 40mm+pb +plaster will be near on 55mm, your old plaster will be likely 20mm overall if it’s traditional wet plaster, maybe more depending how many layers is on, and then you need min 40mm in the brick.

 

get yourself some long coach bolts, smaller plug on the end (length wise) and first hammer it in til it goes no further, followed by tighten up

Edited October 6, 2023 by MikeGrahamT21

[Bonner]

Tend to agree with @MikeGrahamT21 but you could try a 9mm drill into the brick (10mm clearance hole to get the plug through the plaster). It can be a matter of feeling the resistance of materials as you drill

[TonyT]

Or buy some 6mm screwed rod and resin it in.

[saveasteading]

I'd not fix into the external wall but use butterflies behind the plasterboard.

Either the spring ones or those that open out when screwing BUT with the special tool like a rivet gun or it just spins around. I've had school toilet cubicles fixed with them. As below.

Gripits look good but I haven't tried them.

[FuerteStu]

41 minutes ago, saveasteading said:

I'd not fix into the external wall but use butterflies behind the plasterboard.

Either the spring ones or those that open out when screwing BUT with the special tool like a rivet gun or it just spins around. I've had school toilet cubicles fixed with them. As below.

Gripits look good but I haven't tried them.

I've used these before to mount a bookshelf. Amazingly strong fixings. 

 

Don't use an impact driver to fit and tighten them. Use an ordinary screwdriver, or battery one of the lowest setting and keep an eye on the 'feel' of them. So as not to overtighten.

[saveasteading]

Found what i was talking about. With this tool the fixing pulls tight without spinning and so there is no damage to the plasterboard. Then you remove the screw and use it for your radiator. Highly recommended 

[joe90]

I also like those fixings but mine came with a spanner that stopped the plug spinning in the plasterboard. However my new home had a coat rack fixed with these on a dot and dab wall, typically too many coats and the whole lot fell off complete with chunks  of plasterboard 🤯, fixed by filling the holes with plaster and long screws and rawlplugs into the block work. (Radiators full of water are heavy!!!).

[saveasteading]

3 hours ago, joe90 said:

Radiators full of water are heavy!!!).

Especially if someone sits on it. But the brackets are usually big and can take a few fixings, separated.

My mention of cubicles above: the specialist had exclusion  clauses re fixings. I bought the fixings and setting too  and wrote a letter taking responsibility. The fitter was impressed, saying this was the best system he had used. I'm not sure I got the tool back.

[MikeGrahamT21]

Why go to all that expense? Just get some cheap long coach bolts and job done

[saveasteading]

5 minutes ago, MikeGrahamT21 said:

Why go to all that expense

Not expensive and you get to keep the tool. £13 for a Rawl one, or double that at SF.

[TonyT]

3 hours ago, MikeGrahamT21 said:

Why go to all that expense? Just get some cheap long coach bolts and job done

How’s that going to work?

a coach bolt has a thread for a nut ?

not really an expense when you consider what would happen if it fell off, damaged the radiator/floor/leaked/ needed a call out..

 

I’ve used these for 30 plus years and find them great, only literally with the setting tool!  Kit in Aldi/Lidl for the tool and a selection of toggles

[MikeGrahamT21]

 

it’s what they usually provide you with to install a radiator

 

Be no more than £5, job done. All my radiators are installed with these into brick, solid as a rock

[TonyT]

Isn’t that a coach screw?  Makes sense now

[joe90]

1 hour ago, MikeGrahamT21 said:

All my radiators are installed with these into brick,

But what about lightweight aircrete blocks (my second hate for fixing into).

[TonyT]

Use resin and rod

[FuerteStu]

Rather than coach bolts, which have a tendency to shred their grip in masonry, because of the constant thread with no expulsion of debris.. 

 

What about masonry screws, normally used for frame fixings. 

 

[MikeGrahamT21]

1 hour ago, joe90 said:

But what about lightweight aircrete blocks (my second hate for fixing into).

im lucky to not have any radiators on aircrete walls, but yeah would definitely need a different approach to the ones mentioned above.

[Mattso]

Thanks for all the replies, appreciate the input. Only now managed to catch up on the various suggestions. 

 

In terms of expense, I'm not too fussed. The cost of fixing the wall, water leak on the floor and broken copper pipes far outweighs the initial cost. Thought splashing out on the Corefix screws was the answer but it wasn't meant to be as straightforward as that.

 

So the first 3 layers of my 1950s wall are plaster on insulated plasterboard (PB + 40mm PR bonded at factory). Beyond that, it's wet plaster, but as mentioned by another poster, it could be 3mm or it could be as much as 20mm. 

 

Toggle clips are designed for hollow walls and dot and dab, so I don't know if the toggles will expand the way they should. 

 

So to summarise, the options I'd consider are:

 

-9mm drill bit into bricks using 120 Corefix (possibly too short but I could cut off the top and push them into the hole by a few cm)

 

-fill the hole in the brick with resin or quick set concrete, push the corefix plug in, wait for it to set and screw the screw in as intended.

 

-masonry screws, but would have to be at least 100mm long if not longer and might cut into the PB + Insulation under weight

 

-Coach screws maybe. Ideally I'd use the 5 different 10mm holes I've already made into the wall. So they'd have to be 10mm x 100mm min in dimensions. 

 

Cheers.