Electric backbox and dry lining box dimensions?

[Gareth Davies]

I'm about to fit a double electrical socket to a plasterboard wall to replace the present single socket.

The double socket instructions state that I should use a 25mm backbox.

Because the wall is plasterboard, I thought I would use a plastic dry libing box instead. But the lowest size I can find is 355mm. There doesn't seem to be a 25mm dry lining box available.

In terms of the plastic lip around the dry lining box, is a 35mm dry lining box the same as a 25mm metal backbox for the purposes of fitting a double socket?

[Tricky Dicky]

The 25mm back box is the minimum depth for a standard socket, you can get 16mm deep boxes but these are only suitable for lighting switches. It is immaterial whether you use 25mm or 35mm deep boxes. With dry lining back boxes being less used than the metal types there is a reduced range hence the manufacturers produce a 35mm variant to cover all depths. With sockets now combining things like USB chargers and wifi extenders as well as low profile faceplates you might be advised to go for a 35mm depth in case you ever change the socket for one of those mentioned above.

One thing to check on your dry lining socket is if it will fit the plasterboard thickness. I came a cropper with this when I discovered my daughters new build had 15mm thick plasterboard and the dry lining box which comfortably fitted 12mm PB just would not secure in properly.

Richard

[ARW]

You can get dry liner back boxes that will fit into double (2x12.5mm) boarded walls.

[tabbypurr]

backboxes come in all sorts of depths, it doesn't change the dimensions of the front.

NT