Back box depth

[Dave Thornley]

Am redoing the kitchen which has involved altering positions of sockets switches etc. My question is the depth of metal back boxes. For example I had to move the cooker switch only some 60mm to the left. So I chopped out the blockwork, soft grey block, which is fine but as before the back box is now set some 5mm below this blockwork surface. I must point out the wall is blockwork covered with render of about 10mm depth. Taking out the old backbox disturbed some of this render so I pulled any loose render away to be left with firm material. Now after all this rambling my question is do I pack out the rear of the backbox,to bring it level with the blockwork, if so with what or just fi it up against the blockwork. Also how do I fill in the spaces surrounding the backbox so when I get a plasterer around he can crack on with a new skim coat. If it is suggested I fill in the area around the blockwork what should I use. I happen to have a bag of one coat render. And finally will render adhere to previously used polyfilla?

 

[bobasd]

you bring out, or sink, any back box so that the plate sits easy on the finished surface of the wall.

why not post a pic of the situation?

 

[Dave Thornley]

Above is a photo of example.The blockwork has previous render coat of at least 10mm on it and original boxes were sunk so the front of the back box was level with the block front ie set roughly 10mm in from the finished surface.
As I say moving the old box ie the cooker switch box to the right disturded the render leaving a nice hole. My question is do I move the back box further to the front surface by around 10mm? if so could I just use render which would fill the gaps also. Or do I just wire up and let the plasterer sort it. The whole wall is as said going to get a whole new skim.

 

[Notch7]

bring the box forward -you dont have to as longer screws will get over it, but its better to have the box almost flush -easier to locate the screws.

pack out the boxes or fit deeper ones -they are only £1 or so each anyway.

I would ask the plasterer about filling, you might be making more work for him

 

[Dave Thornley]

Am going to put the back boxes so their front edges are just slightly deeper into the wall than the current level of the render, and fill in any large voids with render so he can just put the new skim on.

 

[bobasd]

do as advised by Notch7, and yes you can use whatever mix you have handy to fill the voids.

given your questions, and looking at the pic you kindly posted - why not ask the mods to transfer your post to the elec forum?

 

[Dave Thornley]

Have brought all the boxes out so they sit just behind the level of the current surface so all should be fine for the plasterer's skim coat.
Thanks for the replies guys