Cavity boxes in plasterboard

[Roundtuit]

I've put noggins and metal boxes for switches and sockets where space allows, but where it doesn't, it's plastic cavity boxes .  The question is, to fit before or after plastering? A quick google indicates a split opinion; what's the collective buildhub view please?

[Mackers]

Fit noggins and metal boxes or you'll regret it. Why couldnt you fit metal boxes throughout?

[RichS]

Can't see that it makes a great deal of difference.

Personally I'd fit before skim.

[dogman]

If going for flush metal fittings the plastic will show with some makes of fitting so best to try and fit metal back boxes

[Nickfromwales]

Getting dry lining boxes to stay level during plastering is the issue. 

I'd go for fitting the metal boxes everywhere, using LE exp foam to retrospectively fix the awkward ones into place. You then have the benefit of the one adjustable toggle whereas the dry lining boxes have zero wiggle room for levelling.  

[ProDave]

I am fitting mine after plastering. I have seen them done before, and there is a tendancy for the plaster edge where it meets the box edge to crack and flake.

 

I keep saying it, but if using dry lining boxes. ONLY buy APPLEBY they are the only ones that are truly reliable. Some other makes really are dire.

[Nickfromwales]

33 minutes ago, ProDave said:

I am fitting mine after plastering. I have seen them done before, and there is a tendancy for the plaster edge where it meets the box edge to crack and flake.

 

I keep saying it, but if using dry lining boxes. ONLY buy APPLEBY they are the only ones that are truly reliable. Some other makes really are dire.

Any with adjustable lugs?

[ProDave]

1 minute ago, Nickfromwales said:

Any with adjustable lugs?

Why do you want adjustable? is your wall thickness too great?

 

I will admit a limitation of the appleby boxes is they only work on pb up to 15mm.  The house I have been wiring lately had pb backed with OSB and no he didn't cut an over sized hole in the OSB first, so had socket box holes 22nn thick.  BG plasterboard back boxes fitted but they are the PITA sort where you just touch the lug with the screw and it retreats out of sight.

[Onoff]

Just now, ProDave said:

Why do you want adjustable? is your wall thickness too great?

 

I will admit a limitation of the appleby boxes is they only work on pb up to 15mm.  The house I have been wiring lately had pb backed with OSB and no he didn't cut an over sized hole in the OSB first, so had socket box holes 22nn thick.  BG plasterboard back boxes fitted but they are the PITA sort where you just touch the lug with the screw and it retreats out of sight.

 

Does he mean up/down lug for level?

[ProDave]

Just now, Onoff said:

 

Does he mean up/down lug for level?

You cut the hole in the PB a bit over size so you can wiggle it

 

Or cut it level to start with.

[Nickfromwales]

3 minutes ago, ProDave said:

You cut the hole in the PB a bit over size so you can wiggle it

 

Or cut it level to start with.

Yes boss !

Just asking for boxes which get plastered in and the box fairy nudges them out of kilter. 

[ProDave]

Just now, Nickfromwales said:

Yes boss !

Just asking for boxes which get plastered in and the box fairy nudges them out of kilter. 

An argument in favour of NOT plastering them in.

[Nickfromwales]

Just now, ProDave said:

An argument in favour of NOT plastering them in.

I guess so. Tbh the last lot i decorators caulked around so the gap got painted out. 

[MikeSharp01]

52 minutes ago, ProDave said:

ONLY buy APPLEBY

Such as are available from Screwfix among other places I guess...

[Roundtuit]

Thanks all. I probably have about a dozen boxes on external walls with a 25 mm cavity. All the internals are metal on noggins.  I guess I could have put noggins in, but in a 25mm cavity they would have had to go above and below, with holes drilled for cables and I just didn't have the time to mess about with them as I'm battling to stay ahead of the boarding.

 

I like the idea of a squirt of LE foam behind for a solid fix - top tip!

[CC45]

Ive done as you suggested - poss to use a 35mm box then as well.  Just feels more solid.

 

It is a fiddle & does take time.

[ProDave]

A 35mm box works just fine with a 25mm cavity and the thickness of a piece of plasterboard.