Do 1930 semi's have a cavity wall? My house seems well built and the
party wall goes down below the floorboards. Our next door neighbours
are elderly and when they are talking or listening to the radio the
noise seems overly loud. I should add that we have knocked the
downstairs rooms into one and we (and the neighbours) have open fires.

I suspect that the fires will be the weakspot, however we have just
added some new hole-in-the-wall fires (one in each room) so blocking
the holes wont be an option.

The recesses either side of the fires are only 14 inches deep so adding
a framework and air-gap isn't really an option as we would loose the
character of the place.

Im just suprised that the house being so solid appears to have this
weakspot. Is it just typical of houses of that era and design?