Back boxes and noggins (these are a few of my favourite things)

[Onoff]

I thought you specifically WANTED to use metal back boxes!

 

You'll love my anal approach to fitting pb boxes! I NEVER use a Stanley knife to do the bulk hacking. Multi tool now rather than the padsaw. Gives lovely neat hole. I wrap tape around the blade to the depth of the pb. When cut I neat pva the cut, exposed edge of the hole and allow to dry. Imo it reinforces the edge. Tbh nobody trying to make a living at it would do that!

 

 

[Jeremy Harris]

I opted to fit deep metal back boxes everywhere, really because my experience of using plastic boxes hasn't been great, plus there's a bit more room in metal boxes (handy where you have light switches wired loop in switch where you need room for wagos).  I accept @ProDave's point though, the well-made plastic boxes are probably pretty good now, my prejudice is based on retrofit work on places we've owned years ago.

[ProDave]

  On 05/04/2019 at 13:24, recoveringacademic said:

My tortured finger configuration ? ..... 8 left, of which about 6 have feeling in them (varies a bit each day). I have heard the argument that there is more space in those metal ones....

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Plastic ones are available in 35mm or 55 mm deep. I have never found that not enough space.  If fitting metal boxes I would never fit those silly 16mm deep ones for light switches.

 

There are imho 2 things that can go wrong with plastic back boxes.  The mechanism that latches them in the board can be rubbish so as you go to insert the screw the damned thing just pushes away from you.  Or the embeded brass nut insert on some makes are just a round knurled fitting and at the merest hint of a tight thread the nut will start spinning in the plastic.    You won't have either of these problems with Appleby boxes.

 

Oh and you don't need a box of grommets, which in themselves can be the work of the devil when they pop out just when you think you are finished.

[scottishjohn]

I see no reason why not .

different if you were hard plastering  or having to fix to bricks

used both and if good ones no probs  and you don,t have to worry if sparkie has fitted all the grommets in the knock out holes

knock outs leave very sharp edge ,and can cut cable insulation if it is pulled hard against it 

Yes its  law to fit grommets ,but seen plenty that have got missed or fallen out and hanging on cable leaving cable touching sharp edge  on box 

and you can even buy a box hole cutting tool to fit on your multicut -

makes a nice square hole in plasterboard or brick 

 

Edited April 5, 2019 by scottishjohn

[jamiehamy]

  On 05/04/2019 at 13:14, recoveringacademic said:

 

How do I know what I want until I hear what you, @Onoff @JSHarris  @Bitpipe, @jamiehamy, and others whose technical competence I have come to know and trust say?

(Not forgetting SWMBO ? )

 

I'm sure you mean the word  ' ... considered ... ' respectfully Dave. But in my case, anything electrical is a known unknown as well as an unknown unknown. This is the guy who merrily drills into a wall and wonders - months later - why a light no longer works.

 

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One of the few jobs I left to the spark... Who used (I think Appleby) plastic plasterboards boxes. We did have a conversation and he said he'd use what I wanted, but that was his preference by far. They have been fine? They have an element of adjustment in them which is useful. I dunno - we don't have any loose switches? ? Switch placement I could have done better. You get so caught up and only after a year (!) living here do I notice that switches or sockets could have been better placed. Thankfully these things don't niggle me, just add to the list of 'will do better next time'. 

[Construction Channel]

I was going to stay out of this one but hey,

 

ask your sparks.

 

done.

 

next,......

 

but seriously, there is a good chance he will hate PB boxes, if so there is no point in trying to turn him.

then ask him if you can put the noggins in for him to save him time,

then ask how deep he wants each noggin set back, 

 

its almost irrelevant what a bunch of people on the internet say until you know what he had already planned, (i appreciate that this is necessary research to go into the conversation with a degree of understanding)

 

what are you doing about the boxes on the durisol walls?

[Dee J]

Metal back boxes on noggins have a few advantages... allows first fix to be finished before the boarding starts, avoids having board fixers position the boxes, provides a solid fix for accessories and allows thin accessories sit tight to the wall. But as an electrician I'm happy to discuss options with the customer and work accordingly.

[Construction Channel]

you can also have the boxes closer together with metal boxes.

 for PB boxes you need a fair bit of board between them so it doesn't break when pulling out a stubborn plug

 

FWIW I'm using PB boxes everywhere except where it matters

[ToughButterCup]

  On 05/04/2019 at 20:03, Construction Channel said:

[...]

what are you doing about the boxes on the durisol walls?

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Waiting for experienced people like you to remind me I need  to think about it....

Ermmmmm, metal back boxes, Ed ?

So, if I'm having 12.5mm of plaster, and the wood bit of the Durisol is 20mm or so thick, when do I fix the box? How deep's a back box?

Theres no excuse for sleep at the moment.....

 

[ProDave]

  On 07/04/2019 at 08:00, recoveringacademic said:

 

Waiting for experienced people like you to remind me I need  to think about it....

Ermmmmm, metal back boxes, Ed ?

So, if I'm having 12.5mm of plaster, and the wood bit of the Durisol is 20mm or so thick, when do I fix the box? How deep's a back box?

Theres no excuse for sleep at the moment.....

 

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Are you battening a service void?  Not sure what this "wood bit of Durisol" is?

 

25mm battens and 12.5mm plasterboard makes enough gap for a 35mm plasterboard box to fit into snugly. 

[ToughButterCup]

  On 07/04/2019 at 08:32, ProDave said:

[...]

enough gap for a 35mm plasterboard box to fit into snugly. 

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Perfect.

 

  On 07/04/2019 at 08:32, ProDave said:

[...] Not sure what this "wood bit of Durisol" is? [...]

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The core of Durisol is a concrete lattice and a block of PIR. The rebar goes in before or during the pour.

All that is surrounded by minced up wood which has been boiled, dried and covered with Portland cement. Baked, bashed into shape, dried.

 

To all intents and purposes you can treat Durisol as a piece of wood: cut it with any saw, or chisel or angle grinder. The 'woodcrete' former  (as some refer to it) is 86% air.

[Construction Channel]

If you are planning a service void then I suppose you could use either type of box. Although as it will leave it the perfect depth for a 35mm box you may as well go with metal. 

Another question for your sparks is will 35mm be OK everywhere?  by stairs or places with a lot of 2 way switching you may need an even deeper box. 

 

As an aside when fixing to the durisol do you use plugs or just screw straight in? 

[jack]

We have metal boxes throughout - my electrician was damning of plastic backboxes, but I don't know whether he'd tried the Appleby ones mentioned by @ProDave

 

One thing I did that made things a lot easier was to knock up a jig:

 

 

The front piece is held against the front face of the studs (the nearer stud is omitted for clarity), and the cut-to-length noggin dropped into place and pulled forward against the spacer. This ensures the noggin is installed square.  

 

Optionally, you can add a bit of wood to the bottom to rest on the floor or base of the studwork. Saves you holding the jig in place while you install the noggin, and ensures consistent heights without the need for a measuring tape.

[ProDave]

If using the jig described above by @jack you could add 2 legs to get all socket dwangs noggins at the correct height 

[CC45]

some fittings may need deeper back boxes - maybe 47mm - individual room stats are pretty deep, I put in 47mm boxes for an easy life - they must be tight with 35mm back boxes.  Sensible to check.

[Onoff]

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