Skim too thick for plasterboard back boxes

[Thorfun]

greetings. I've started to cut out and fit back boxes but I'm finding that our makeup of 12.5mm plasterboard and skim is about 16mm. I'm using the Appleby back boxes as recommended by @ProDave but I don't get the satisfactory 'click' when the clips fit in place. is that a problem?

 

the back boxes are apparently designed and tested specifically for dry wall/plasterboard, with a thickness of 6.35-15mm. so I'm about 1mm too thick.

 

is there a way to make it fit so they click in to place? or am I being special and worrying about nothing as usual?

 

 

 

[joe90]

I am not an expert but that seems awfully thick for a skim, sand it back? 🤷‍♂️

Edited November 7, 2023 by joe90

[MikeGrahamT21]

Snip the lugs off or buy the deeper box version, either should do the trick

[Thorfun]

6 minutes ago, joe90 said:

I am not an expert but that seems awfully thick for a skim, sand it back? 🤷‍♂️

might be tricky to sand back just around the back box though! might be easier to cut a bit off the back of the plasterboard!

 

I thought a skim was 3mm with the 2 coats of plaster. at least that's what I worked all our measurements to. which makes me wonder why the back boxes aren't made for 16mm thicknesses. unless these days they don't expect anyone to skim the walls and just tape and fill.

 

or maybe I need to find another brand of back box that will do slightly thicker wall makeups?

[Mr Punter]

These go to 17mm:

 

https://www.tlc-direct.co.uk/Products/MTMDLB1.html

[Thorfun]

2 minutes ago, MikeGrahamT21 said:

Snip the lugs off or buy the deeper box version, either should do the trick

does snipping the lugs off not reduce the effectiveness of the box being held in place?

 

also, according to the Q&A here https://www.screwfix.com/p/appleby-1-gang-dry-lining-knockout-box-47mm/83270 the 47mm boxes are also meant for 6.3mm - 15mm thicknesses

[Thorfun]

1 minute ago, Mr Punter said:

These go to 17mm:

 

https://www.tlc-direct.co.uk/Products/MTMDLB1.html

thank you! any idea of the quality? when reading threads about plasterboard back boxes @ProDave mentioned that some are a lot poorer than others and he only uses Appleby as they're good quality.

[MikeGrahamT21]

3 minutes ago, Thorfun said:

does snipping the lugs off not reduce the effectiveness of the box being held in place?

 

also, according to the Q&A here https://www.screwfix.com/p/appleby-1-gang-dry-lining-knockout-box-47mm/83270 the 47mm boxes are also meant for 6.3mm - 15mm thicknesses

It will but you can work around it, dot of silicone on the lug track to hold in place, and once you’ve got the face plate screwed it it won’t move anyway. The other thing you could do it shorten the track guides slightly, this will give a longer run and give you the satisfying click

 

ive butchered a few of mine over the years and they’re still where I want them

Edited November 7, 2023 by MikeGrahamT21

[Mr Punter]

Sorry no idea of the quality.

[Thorfun]

34 minutes ago, MikeGrahamT21 said:

It will but you can work around it, dot of silicone on the lug track to hold in place, and once you’ve got the face plate screwed it it won’t move anyway. The other thing you could do it shorten the track guides slightly, this will give a longer run and give you the satisfying click

 

ive butchered a few of mine over the years and they’re still where I want them

Thanks. Although when you have over 100 to fit that starts to seem like a daunting task! 😂

[ProDave]

Is there anything restricting the depth in the cavity?  the time I find the lugs don't click into place are when the back end of the yellow lug has hit the back of the cavity.

 

Get a long flat screwdriver behind the bit sticking out either side of the screw and you can sometimes pull or lever it forwards that last bit it needs.

 

I doubt all your cut outs will be this thick, how many have you cut so far?

 

P.S I usually do the cut outs before the spread arrives.

[ToughButterCup]

27 minutes ago, Thorfun said:

..... when you have over 100 to f  it that starts to seem like a daunting task! 😂

 

Ah not to worry: if your experience is anything like mine, most of the sockets will be

• in roughly the right place,
• but in-the-wrong-place  in SWMBO's opinion.  
• and you'll need at least six multiple socket extensions to placate her
• but the dog(s) will object and chew those sockets . 
• then the grandchildren will be inserting pens in the unprotected sockets
• and you'll be glad you fitted RCBOs

 

 

[Thorfun]

2 minutes ago, ProDave said:

Is there anything restricting the depth in the cavity?  the time I find the lugs don't click into place are when the back end of the yellow lug has hit the back of the cavity.

nope. this particular wall is 140mm deep so nothing behind.

 

2 minutes ago, ProDave said:

Get a long flat screwdriver behind the bit sticking out either side of the screw and you can sometimes pull or lever it forwards that last bit it needs.

ok, will give that a try as well

 

3 minutes ago, ProDave said:

I doubt all your cut outs will be this thick, how many have you cut so far?

just 2 to get ready for the AC install tomorrow! many many more to go. 😉

 

3 minutes ago, ProDave said:

P.S I usually do the cut outs before the spread arrives.

way too late for that. i did ask the plasterers and they, obviously, said they'd prefer to not cut out before they skim. and as they did the boarding i wouldn't have had time anyway.

[MikeGrahamT21]

51 minutes ago, Thorfun said:

Thanks. Although when you have over 100 to fit that starts to seem like a daunting task! 😂

True but think of the money you’ll save!

[Alan Ambrose]

You can make little cutouts at the back of the plasterboard very quickly with a plasterboard saw to make them work, particularly if there's not many to do. Some of my walls here have two sheets of PB, so 25mm thick. Alternatively, for a few mm, you can just be gentle and pull the screws up tight without the tabs latching, and they'll hold the whole thing in place fine.

[Thorfun]

2 hours ago, Alan Ambrose said:

You can make little cutouts at the back of the plasterboard very quickly with a plasterboard saw to make them work, particularly if there's not many to do. Some of my walls here have two sheets of PB, so 25mm thick. Alternatively, for a few mm, you can just be gentle and pull the screws up tight without the tabs latching, and they'll hold the whole thing in place fine.

i wonder how removing cutouts from the back will effect the strength of the PB? without the paper there will it make it a bit brittle in that area where the lug is holding the back box in place?

[Thorfun]

i haven't bought all the back boxes yet. so i'm tempted to try those Knightsbridge ones @Mr Punter linked at TLC to see if they work and what sort of quality they are.

[markc]

28 minutes ago, Thorfun said:

i wonder how removing cutouts from the back will effect the strength of the PB? without the paper there will it make it a bit brittle in that area where the lug is holding the back box in place?

That’s called over thinking and engineering in a problem

[Kelvin]

That’s really thick plaster. I have two coats and it’s nowhere near that thick. We had this very debate too and I cut out all the holes beforehand because the consensus was it can cause this very problem you have. It then means all the boxes are also plastered in. At least you’ll have very clean boxes. 😂 

[Thorfun]

26 minutes ago, markc said:

That’s called over thinking and engineering in a problem

pretty standard for a self-builder, no? 😉

[Thorfun]

19 minutes ago, Kelvin said:

That’s really thick plaster. I have two coats and it’s nowhere near that thick. We had this very debate too and I cut out all the holes beforehand because the consensus was it can cause this very problem you have. It then means all the boxes are also plastered in. At least you’ll have very clean boxes. 😂 

i'm actually happy with the thick two coats. at least i know it's solid!

 

i love the silver lining of having clean back boxes. i'll focus on that. 😆

[Gone West]

2 hours ago, Thorfun said:

i haven't bought all the back boxes yet. so i'm tempted to try those Knightsbridge ones @Mr Punter linked at TLC to see if they work and what sort of quality they are.

I bought Knightsbridge plasterboard boxes from TLC for my new build and ended up replacing them with Appleby. I only bought the Knightsbridge ones because I was getting a lot of stuff from TLC and they didn't have Appleby. Knightsbridge were crap, so many of the sliding lugs broke off that I just chucked them.

[Thorfun]

24 minutes ago, Gone West said:

I bought Knightsbridge plasterboard boxes from TLC for my new build and ended up replacing them with Appleby. I only bought the Knightsbridge ones because I was getting a lot of stuff from TLC and they didn't have Appleby. Knightsbridge were crap, so many of the sliding lugs broke off that I just chucked them.

thank you so much for this! i will now definitely stick with Appleby and figure out the best way to reduce the thickness of the plasterboard/skim make up.

[Kelvin]

How many of the Loxone back boxes do you need? I have some spare I could send you. 

[Nick Laslett]

I was just looking at stud wall pattress boxes. I have used double boards for my wall construction, so need 22.5mm depth. 
 

https://www.ukelectricalsupplies.com/norslo-1-gang-47mm-dry-lining-box.htm

 

Norslo DL147N have 30mm depth

 

I thought I’d post this for anybody looking for this in the future.