in line with stw etiquette of asking on a cycling forum, instead of asking a professional for fear of seeming like a numpty, everywhere i’ve looked only seems to sell 25mm double gang back boxes, but plenty of 16mm single ones available, why is this? 25 mm will stick out from the wall a fair bit, do i really have to take some out of the bricks? don’t really want to have to ask a real electrician, without having checked with the hive first…

Your not surface mounting are you. Even 16mm surface mounted looks awful. It screams bodge

You can get 16mm recessed double boxes online but if your knocking a hole in bricks might as well stick in whats easy to get.

Singles are typically for a light switch not a socket these days so don’t need to be as deep.
Get you bolster chisel out and do it properly.

Get one of those yellow plastic drilling guides, makes it so much easier.

A patrice guide template. Those went out with the arc didnt they ? Hammer and bolster for plaster and lathe/blockswork and a jab saw for plasterboard

Appleby still make a 16mm metal 2g back box

http://www.sparksdirect.co.uk/16mm-deep-two-gang-flush-box

If the back box is going it be used for sockets then you will need to use at least a 25mm depth back box. 16mm back boxes are only designed for lighting and even then it’s generally 25mm boxes that are used as 16mm are only really any good if there’s just the 1 cable in the light switch.

cheers chaps, no its not surface mounted, yes its into old plaster then brick, didn’t really fancy chopping into the brick, loosening the mortar and the rest of the old plaster etc. i wonder if these days its all done with dot and dab, in which case 25mm is perfect…

As jdean says. I run the live feeds to the switch rather than loop into ceiling roses, making it easier to retrofit alternative lighting but it has the downside of putting a lot of wires in the backbox.
Don’t forget to use open grommets to fill the knockouts (avoids chafing).

@ trail rat – thirties brickwork here, so I’ve found one useful. Bro is a time-served house-bashing sparkie and used one. I’ll follow his example, unless there’s something newer available?

@rwamartin

I run the live feeds to the switch rather than loop into ceiling roses

are ceiling roses considered a bit old school these days or is it just a personal preference?

Hammer and bolster for plaster and lathe/blockswork

What century are you living in?

SDS Socket cutter adapter….

cheese knife would cut that block though 😉

I used that socket cutter. It’s great for lightweight blocks. Takes seconds to make really nice holes. It won’t touch old bricks though. That pattress drill jig would have been handy. The three I had to cut into the brick are going to need a little bit of extra plastering

I used the yellow plastic thingy recently, it happened to be cutting into a concrete block next to a breeze block. I think the difference in hardness of the two and the mortar between would have given problems to anything alse.

(edit)
http://www.diy.com/nav/fix/power-tool-accessories/router-bits/jigs/B-and-Q-Patress-Jig-12848800?skuId=13359506