gang box size

[Marco1976]

Hi,

I am removing plasterboard and insulation that was put in to reduce noise through a party wall. The existing sockets are dry lining sockets. I want to sink these in the wall so I need suitable backboxes. I have seen two siezes, 25mm and 35mm. Which size should i use? I am assuming that the 25mm ones are for swicthes.

 

[GaryMo]

25mm are standard depth for flush mounted backboxes for either switches or sockets.

If you intend to fit flat plate sockets then it would pay to fit 35mm depth backboxes for a little extra room.

 

[Paul_C]

Given the choice, I would use 35mm for sockets anyway for the extra wiring space. 25mm boxes are pretty much the norm for sockets, but can be cramped for space even with just two 2.5 T&E cables. If you have any with a third cable for a spur, it's even more restricted.