How thick is my wall

[beejay]

We're rewiring a 1962 built semi detached house and would like to chase some sockets into the wall between us and next door. I'd like to be sure on the thickness of this wall before drilling into it. It is built of brick and supports the upstairs floor joists at the front of the house so I'm assuming its at least two courses thick (unless the joist carries on through into next door?). This is a pic of the attic wall...



The fact you can see the "ends" of bricks suggest to me they're tying together two courses of brick (English bond?) unless they were using up a load of halves where they wouldn't be seen There aren't any gaps that I can reach in to feel how thick the wall is. Anyone able to help?

[beejay]

The sockets aren't going into the attic, just thought it may be a useful photo as it's the only place with all the brickwork on show. Planning to put 5 sockets in spread amongst the various rooms.

I've been doing the ones on the other walls with a grinder to cut through the plaster cleanly, chain drilling to the correct depth then a SDS to chisel the brickwork away.