Removing the back of a dry lining box - good or bad?

[Rockingit]

Just wondering what peoples thoughts are on completely removing the back of dry lining boxes to be able to accomodate cable better when it's a tight squeeze and too many cables (for example if you've a three gang switch plate all fed separately from the switch - so that's six cables to terminate).

Personally, my thoughts are that if the plates are set with a thin bead of intumescent sealer then it's no big deal, but curious for the input of others.

 

[cagedanimal2010]

is a deeper box not an option?

 

[DaveyD]

I usually loop in switch and if more than 5 cables in there I get a 47mm Dry box

 

[GLENNSPARK]

but its like only 1mm...or 1.5mm.....not much weight in em is there?.....the thing i always look out for....is trapped cables...especially on metal boxes where 3.5mm screws can cut into em n all....i always bunch em up towards the middle before offering the front up to the box.....seen a few that have clearly been trapped and have been taped up...rather than crimping............

 

[ruston]

47mm especially for those nice fcu's, and they are better for the thicker boards and lime lathe.

 

[GLENNSPARK]

FCUs can be a pig sometimes.....

 

[thomasn]

Cable sheathing must be within the back box same as a junction box. If the back was cut out this would be a fail on inspection or verification

 

[ruston]

under the wall units in a kitchen , the tiler has covered the fixing holes , it's in the corner . Can't wait for the next one lol.

 

[Engineer54]

5 & 6 cables going into a single wall back box!!! I can see that a lot of thought went into the design of these installation light circuits! And then cuts the back off the box to get enough room for them!! ...Geezus!!!

 

[Rockingit]

5 & 6 cables going into a single wall back box!!! I can see that a lot of thought went into the design of these installation light circuits! And then cuts the back off the box to get enough room for them!! ...Geezus!!!

In a property where almost the entire lighting stock is wall uplighters, and more 2&3 way switching than a tranny bar, you need to adapt! Not to mention that the whole-house HVAC is boost triggered from the lighting zones as well. Loop-in-out on a ceiling is just a distant dream, not a design failure, thanks all the same.

 

[topquark]

Can't believe you'd be doing this unless you had a good reason .... so ....

As it's a dry lining box (and hence easily removable) can you not use some maintenance free connectors behind the junction box (maybe the inline connectors by the sponsor on here) enabling you to use a normal (intact) lining box. Still a bit of a bodge though.

 

[Rockingit]

Can't believe you'd be doing this unless you had a good reason .... so ....

As it's a dry lining box (and hence easily removable) can you not use some maintenance free connectors behind the junction box (maybe the inline connectors by the sponsor on here) enabling you to use a normal (intact) lining box. Still a bit of a bodge though.

That's kind of where I'm at with it, yes. Thankfully there are only two or three plates where this will be a serious issue, and thankfully on the internal stud, not the external. If it was the latter I think I'd just throw in the towel now as there's only a 20mm service space in between plasterboard and vapour barrier! For example, (from memory) there's one double gang plate which is going to need to have a 6g switch plate - internals x 2 , externals x 2, landing x 2 (2way). I think I make that eleven cables. No chance of having designed it as loop rather than switch feed due to a hundred things I won't bore you with. So what's a Sparks to do? You have to think outside the box (pun definitely intended!). Not ideal, not best practice, but to try to cram that lot into a deep box even and it's asking for trouble.

So my thoughts are to try to get the crimp joints outside the box, in the stud hollow, make as neat a job of dressing the rest as possible outside, shrinking any major sheath failings, and bringing the S/L's into the box. But even with 11 + 2x3cores there isn't gonna be a lot of plastic left around the gromits!

 

[topquark]

As it's plasterboard, may be worth making yourself some "more room". IE remove a larger portion of PB around the boxes between the studs (600mm on centres usually). That'll give you more room to make a better job of the perm joints (as presumably not much cable free to pull through). You can then attach some batten to the side of the wall studs to reattach the PB, fish through the cable and terminate as normal. Then use a bit of easi-fill/tape to make good the joins (also saves damaging any of the PB around the boxes).

Less likely to damage the vapour barrier that way (and if you do, it's easily fixed). Or just use that as a fall back position if it goes pear shaped.

 

[Rockingit]

My fall back position is the pub. End of. :54:

 

[Rockingit]

Oh, and I DID design for this - there's loads of cable slack!!

 

[GLENNSPARK]

well i cant get my head round this properly ....your on about plasterboard....then on about wrecking an enclosure??.....i bet if you had gone away for a bit...had a cup of tea then come back, made a decision and gone to it it would have been sorted.......

 

[nickblake]

new build or referb if there is decoration to do the with all those cables i would go for a deep galve back box try and secure some wood to fix to and go for a 2 gang back box the only time i knock out the back of the box is when im making an access panel for a plumbers isolation valve then a blank plate on it

 

[GLENNSPARK]

new build or referb if there is decoration to do the with all those cables i would go for a deep galve back box try and secure some wood to fix to and go for a 2 gang back box the only time i knock out the back of the box is when im making an access panel for a plumbers isolation valve then a blank plate on it

thank god an answer....that sounds like "it just might work" by J.L. Picard...lol...but yes...a good one Nick.....

 

[Rockingit]

well i cant get my head round this properly ....your on about plasterboard....then on about wrecking an enclosure??.....i bet if you had gone away for a bit...had a cup of tea then come back, made a decision and gone to it it would have been sorted.......

Plenty of tea and head-scratch time on this one; it's just a complete pig of an architects design and absolutely nothing is 'ordinary'. I'm having to make custom bits and bobs all over the place. There's more cable in the garage alone than half the flats you'll find!

Nick - reason for not using your method (as I would also normally do) is because no-one knows what the finished internal floor heights will be yet (by as much as +/- 100mm), so to fix a box on a noggin was just too much of a risk. There are actually parts of the build where we've done just that, but where we know what's happening with the floor.

I think what I can see happening is a bunch of MF junction boxes dropped into the stud, and bringing S/L's into the boxes in the usual way; that would work.