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!!