burying plastic backboxes

[dandt]

If you 'chase in' a surface mounted cable, are you allowed to bury a plastic backbox thus creating a flush fitting (or must it be a metal back box). My question is partly curiosity and partly for use in the future as different parts of this house get improved / plastered / decorated.
Thanks
I hope this isn't considered a stupid question. Someone else has done one of the light switches like this.

 

[333rocky333]

No reason why not ,but you will have no flange, so will be hard to decorate etc.

Metal boxes are smaller than the accesories to allow for this and allow adjustments to level up normally.

 

[dandt]

thanks good points about the metal back boxes
but good to know I wouldnt be breaking any regulation.
If I used a metal back box would it have to be earthed to just the socket/cable.

 

[ban-all-sheds]

No reason why not.

IMO it does not comply with the Wiring Regulations.

134.1.1

 

[333rocky333]

Regarding the earth, Debatable that, I personally always put a link between socket and box, however some only do under certain circumstances..

 

[Chri5]

Builders depot sells the above rubber 'forms'.

The sit inside a sunk metal back box and allow for a nice finish with the plaster all the way up to the box line.

Saves spending 10 minutes cleaning out half a kilo of dried in bonding plaster from a box.

 

[ban-all-sheds]

but good to know I wouldnt be breaking any regulation.

You would be breaking 134.1.1

 

[ban-all-sheds]

Builders depot sells the above rubber 'forms'.

Of no use whatsoever if you've buried a plastic surface box.

And anyway - surely you only get "half a kilo of dried in bonding plaster" in a box when a plasterer has gone over an entire wall, not when trying to patch up to the edge of a box you've installed in a finished wall, and that thing won't stop that.

 

[Chri5]

Of no use whatsoever if you've buried a plastic surface box.

I was trying to offer a easy DIY solution for metal boxes, which the OP seems reluctant to use.

And anyway - surely you only get "half a kilo of dried in bonding plaster" in a box when a plasterer has gone over an entire wall, not when trying to patch up to the edge of a box you've installed in a finished wall, and that thing won't stop that.

No it won't, but it will act as a form and should allow the plaster to be removed from inside the box cavity with the advantage that the plaster will be formed to the box footprint.
Saves 5 minutes of stanley knife crafting of the edge line, and prevents further patching when plaster lumps pull away beyond the box line.

Since box patching is an acquired skill, is it wrong to suggest a product that removes the skill requirement ?

 

[holmslaw]

..

 

[ban-all-sheds]

I was trying to offer a easy DIY solution for metal boxes, which the OP seems reluctant to use.

Ah - OK. Since he wasn't asking about plastering problems with metal boxes I thought you were proposing it in response to "you will have no flange, so will be hard to decorate etc".

No it won't, but it will act as a form and should allow the plaster to be removed from inside the box cavity with the advantage that the plaster will be formed to the box footprint.
Saves 5 minutes of stanley knife crafting of the edge line, and prevents further patching when plaster lumps pull away beyond the box line.

Since box patching is an acquired skill, is it wrong to suggest a product that removes the skill requirement ?

No, if patching is what's involved, and I might well get one myself for that. But have you ever used it when a wall is being fully plastered? It's not what the maker targets it for, and as it's made of rubber I wonder how well it will stand up to lots of plaster being trowelled on...

 

[Chri5]

I also saw a plastering trim for switches and sockets today.

Basically you fit the back box, fit a pre moulded bead and then plaster.

The result is a recessed back box with a plastic lip level with the plaster finish, for a perfect flat finish they would work well.
The flat faceplate designs tend to have no give and require a perfect wall or flat surface. Plastic sockets and switches seem to be more tolerant of imperfect walls.

It looked very similar to tile edge trim in square or rectangle format with a net like base to fix to the pre plastered wall.

 

[ColJack]

perfect flat walls round switches and sockets? that's what steel rules are for.. make great scrapers to level it off..

 

[Johnmelad502]

Builders depot sells the above rubber 'forms'.

The sit inside a sunk metal back box and allow for a nice finish with the plaster all the way up to the box line.

Saves spending 10 minutes cleaning out half a kilo of dried in bonding plaster from a box.

Nice one Chris, I can see how handy that will be in certain circumstances. Cheers for the tip...

 

[dandt]

On balance I will probably leave plastic boxes surface mounted
thanks again