EricP wrote:
Two 1980 semis. Concrete block construction, london brick outer walls.

How thick is the party wall likely to be please?

Most likely 2 x 100mm plus a 50mm or 75mm cavity. Or solid 215
blockwork. Or 9" brick.

Or measure from halfway between yours and your neighbour's window.
Measure from the internal reveal to the wall. Subtract the second from
the first & multiply by 2 (assuming that the plaster on the reveal is
the same thickness as that on the party wall).
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