Dave Liquorice wrote:
On Mon, 13 May 2013 20:25:22 +0200, imanc wrote:

There's a lumpy mess and some cracked brick that is stil somewhat
firm, and the back box doesn't seat right.

Get one fixing ready, lob in some stiffly mixed old plaster, push in
box and use fixing. position and leave.

With one recess the back box is about 5mm too deep.

Is that a problem? You can get longer accessory screws if the ones you
have are too short.


Having the back box set 3mm behind the plaster finish is the correct way to
install back boxes for use with flat plate switches and sockets.

--
Adam