New Electrical Socket Installation

Roundabouts

Hi, I'm trying to replace some bog standard plastic electrical sockets in one of my bedrooms with brushed-steel flush ones. I've removed the old plastic socket and there's a 25mm metal mounting box set in the wall. Unfortunately the new sockets require a deeper mounting box so I've bought a 35mm metal mounting box and a 35mm dry lining plastic box. I've removed the old 25mm mounting box and am left with what is shown in the photograph.



As you can see behind the plasterboard there is a breeze block. I need to go back about another 10mm to fit a new 35mm mounting box in. Would a jigsaw with a metal blade be the best thing to use to cut the depth of 10 or 15mm into the breeze block?

And If I do this will I be able to fit the 35mm metal mounting box to the breeze block? It might crack when I try to fix the metal mounting box to the thinned breeze block? So the plastic 35mm dry lining box would be best as this doesn't involve drilling? Or is there some better way of doing this altogether? Thanks for any advice.

jimi_man

Not quite sure how you intend to use the jigsaw? I would have thought that the blade would snap as soon as it strikes the breeze block. Not really the ideal tool in my opinion.

You only have to go in 10mm, so I would just chip it out with a suitable tool to the required depth by hand, drill a couple of holes for the back box with some suitable wall plugs and voila. It's not going to make any appreciable difference to the strength of the breeze block, I'd like to think they are a bit stronger than that!.

Roundabouts

jimi_man wrote: »

Not quite sure how you intend to use the jigsaw? I would have thought that the blade would snap as soon as it strikes the breeze block. Not really the ideal tool in my opinion.

You only have to go in 10mm, so I would just chip it out with a suitable tool to the required depth by hand, .

Good point. I thought perhaps the jigsaw might avoid breaking the breeze block which might happen if I start chipping away at it with a cold chisel and club hammer?

jimi_man wrote: »

, so I would just chip it out with a suitable tool to the required depth by hand, drill a couple of holes for the back box with some suitable wall plugs and voila.

So you'd go for the metal mounting box option then? It's just if I use the plastic dry-lining mounting box then I won't have to attach it to the breeze block, it just 'clips onto' the plasterboard at the front I think.

jimi_man

From a personal perspective as a DIYer not an electrician, I don't like the plastic boxes into plasterboard. I would have thought that every time you plug or unplug something it would stress the plasterboard, and wear it away so the box could become loose. I would prefer to screw it into something more substantial, like the wall.

Of course I might be wrong, and they may be fine.

Roundabouts

jimi_man wrote: »

From a personal perspective as a DIYer not an electrician, I don't like the plastic boxes into plasterboard. I would have thought that every time you plug or unplug something it would stress the plasterboard, and wear it away so the box could become loose. I would prefer to screw it into something more substantial, like the wall.

Of course I might be wrong, and they may be fine.

I've just checked and the existing hole in the plasterboard is a bit bigger than it really should be. So if I fit the plastic mounting box into it it might be a bit loose even after it grips the plasterboard. So you're right, the metal mounting box fixed to the breeze block at the back is probably the best way to go.

fluffpot

breeze block is nice and soft, so a doddle to knock it out - compared to engineering brick, say. Just make sure you get the back nice and flat so the box doesn't sit wonky

Ruski

That's a thermalite/celcon block - soft as shute - use on old chisel to dig out the extra 10/15mm - wont take you long - done hundreds.

HTH

Russ

27col

Agree with Ruski,Thermalite/Celcon blocks can almost be scraped away with your bare hands. Easy enough to do with an electricians bolster. A bit dusty, but not a problem at all.

Roundabouts

fluffpot wrote: »

Just make sure you get the back nice and flat so the box doesn't sit wonky

Thanks for all the great advice from everyone. Maybe first of all I could use a drill to drill the block in numerous places to a uniform depth of 10mm. Before then using a hammer and bolster. Doing that might help me to get it flat at the back?

googler

Might it not be easier to find alternate brushed steel sockets which require a 25mm box, not a 35mm?

jimi_man

I'm pretty sure you won't need to do any of that. Just try scraping it away with an old chisel or something with your hands, rather than a hammer and bolster. It's not brickwork, it shouldn't need that much force.