Christian McArdle:
One reason is that the wall construction was very different, with lime
mortars and flexible materials used in order to mitigate the larger degree
of settlement that foundationless buildings had.

Is it not more a case of settlement not mattering so much because lime
mortar was all they had?

If you built a modern wall
using cement, rigid insulation and gypsum plaster or boards, it would crack
to buggery in a couple of years (or even weeks/months). The old Victorian
buildings just settled in a different shape to that built, but the materials
flexed to suit.

Our Victorian semi seems to have settled quite a lot before the final
fit had even been done, judging by one upstairs doorway that is a good
inch lower on one side. The original architrave has just been cut to
fit a less than 90 degree corner on one side and the door is trimmed to
fit..

If this settlement had happenned later there would be a big gap at that
corner. We are blessed with brick walls upstairs, even where they
aren't built on top of brick downstairs, I presume (and hope) there are
some really big bits of timber under them somewhere! The result is a
somwhat bouncy house, even a 2 year old running around in one room
makes the floor shake in another.

But ours is one of a long row, none of which has fallen down yet, so
I'm not worried.

Andrew