Fixing kitchen wall units to 72mm Plasterboard/Insulation Wall

[RJRock]

Some advice please:

I'm looking to fix kitchen wall units to (72mm total width) Plasterboard /Insulated backed Walls.

The 72mm walls are dabbed to either lathe and ply walls (with air gap) or to Solid brick (not cavity) walls (with air gap).

What is recommended: a hanging rail for both types of wall (trying to find studs on the lathe and ply wall)?

OR

Using Torx masonry screws for fixing a hanging rail to the PB with brick wall behind?

Any advice welcome. Thanks

 

[foxhole]

If rear wall is ply then long wood screws with hold to ply and as you mentioned masonry screws for brick .

 

[sxturbo]

These for the dot and dab to brick walls

https://www.screwfix.com/p/corefix-...zZXqugO4Fx5yMynN4HEaAunGEALw_wcB&gclsrc=aw.ds

These for the plasterboard to lathe

Use gripit blue fittings

 

[RJRock]

72mm Insulated PB

• RJRock
• 11 Dec 2020

Masonary Screw Torx

• RJRock
• 11 Dec 2020

The PB is fixed to the insulation and insulation side dabbed to walls.

Picture of torx screws - These would go through the PB/Insulation (72mm) air gap (25mm ish) and into wall, to fasten hanging rail for cabinets. A bit afraid of crushing PB/Insulation though. I'd be looking to use wood screws through the 72mm and airgap into any wooden uprights I can detect in the lathe wall. (Foil on insulation messes up the stud detector a bit.)

SXTurbo - not sure the fastenings you suggested would be better as I may not have explained things clearly in my original post.

 

[dontbelieveawordofit]

you wont have enough control over those screws to get the right torque.
they’ll either stop too slack or so tight they’ll pull the bracket in to the board.
also imo i think the gap is too great and the screw and bracket will sag under the weight . id use metal wall rails to spread the load.

 

[sxturbo]

That's not going to be any good, you will be relying on the screw to do the weight carrying and at 4" the cantilever on the screw will be far to much, the cabinets will be coming down.

The correct thing to do is to drill large holes say 15-20mm and get metal spacers machined that are 100mm long, when you screw the cabinet brackets to the spacers and to the wooden uprights it will bunch up tight and provide a solid fixing which you won't be relying on a screw on a cantilever.

Plasterboard requires the weight to be spread over a large area otherwise it's very weak.

 

[RJRock]

you wont have enough control over those screws to get the right torque.
they’ll either stop too slack or so tight they’ll pull the bracket in to the board.
also imo i think the gap is too great and the screw and bracket will sag under the weight . id use metal wall rails to spread the load.

Hi and thanks. When you say use metal wall rails to spread load, I assume you mean the 1 or 2 m metal rails (e.g from Screwfix). I was going to use those anyway (top and bottom of wall units), just a question of the way I'd fix the spreader rail to the PB. Would torx screws for brick wall fixings and woodscrews to wooden uprights be ok? SXTurbo advises spacer through to wall behind PB/Insulation which seems ideal.

 

[foxhole]

I found it no problem at all to drive those screws perfectly into wall .

 

[dontbelieveawordofit]

I found it no problem at all to drive those screws perfectly into wall .

into a wall . or trying to fix something to a plasterboard with foam behind it?

 

[foxhole]

into a wall . or trying to fix something to a plasterboard with foam behind it?

Both

 

[dontbelieveawordofit]

Both

always find the need to fix things weighing potentially 40kg+ to pb walls with little or no support behind do you?
be a poppet then and nip round to show him what to do.

 

[RJRock]

These for the dot and dab to brick walls

https://www.screwfix.com/p/corefix-...zZXqugO4Fx5yMynN4HEaAunGEALw_wcB&gclsrc=aw.ds

These for the plasterboard to lathe

Use gripit blue fittings

Just realised if Grippit blue ok for PB then as it needs a 25 mil hole to insert and activate the 'wings' surely that would work with pb backed with insulation? I've got an offcut to see if the insulation gives and allows the 'wings' to move into place.

 

[foxhole]

always find the need to fix things weighing potentially 40kg+ to pb walls with little or no support behind do you?
be a poppet then and nip round to show him what to do.

All my external walls are insulated plasterboard, had no problems fixing to them , guess some people are just smarter than others .

 

[endecotp]

Just realised if Grippit blue ok for PB then as it needs a 25 mil hole to insert and activate the 'wings' surely that would work with pb backed with insulation? I've got an offcut to see if the insulation gives and allows the 'wings' to move into place.

I have a feeling they sell a special tool for that, or something. (I must have read it on here, I've never used those things myself.)

 

[bsr]

It's called an undercut tool.

https://www.screwfix.com/p/gripit-15mm-undercutting-tool/3358j