Hi,

I want to extend the ring mains in my (1930's) house to add two double
sockets to a room. I've got the floorboards up and know where the new
cable needs to go. However, the thing that's stopping me going ahead is
the fact that the existing cable appears to be ever so slightly thicker
than the 2.5mm^2 that I was going to use. It is also multi(6)-stranded
instead of single-stranded. Is this to be expected with older wiring (I
believe a rewiring was done in the 70's)? There is a 32A MCB at the fuse
box so I thought that 2.5mm^2 would do the job but having seen the
existing wire I now have doubts. I don't want to weaken the installation
by using wire that is too thin.

After a bit of Googling it seems that 4mm^2 cable might be used in a
radial installation but I disconnected the wire between two sockets in
the room and they both still worked - does this allow me to conclude
that I have a ring mains? Also, 4mm^2 cable doesn't seem to be available
from B&Q, etc. - the next size up is 6mm^2.

Maybe the fact that I'm having to ask these questions suggests that I
should get in an electrician?!

Cheers,
Grant