Houses built before the war are likely to be lime mortar,

Not all.

as cement was
too expensive for normal use, and ivy will penetrate the mortar and
loosen the bricks.

Not so in our case. Mind you, come to think of it, when we moved in here in
the early 1960s we re-pointed the house with a mastic sand and linseed oil
mixture which has proved durable, strong, waterproof and everything else one
could wish.

I planted ivy on two corners of our house many years ago.

Recently, after surgery which might have limited my arm movement, I decided
that one day we'd get too old to maintain it (I'd go up a ladder every year
in August and pull off the loose strands, thus keeping it in trim). It was
important to do something about it before we were incapable. It was also
important to keep it from the top of the newly built carport, I couldn't
reach over that.

I pulled off as much as I could then cut it thinner branches with secateurs
then larger ones with croppers and finally cut through the trunk with a saw.
Spouse made large holes in the drive and pulled out as much root as he could
then concreted over the earth.

That was in August this year. So far there has been no re-growth (he did go
quite deep down). There has also - to date - been no ill effect on the
house.

More importantly, there was never any damp caused by the ivy on the house
wall. The ivy leaves shed water well away from the wall, protecting it.

I've noticed that when ancient walls have ivy growing on them it's always
the green-covered parts which stand, the exposed parts disintegrate.

The main problem with ivy on the house was when it got into and behind the
wooden gutters. It blocked the gutters which were inadequate anyway and
overflowed and as the stems grew thicker it prised the guttering away from
the roof tiles.

Ivy growing under and out of the tiles themselves wasn't a problem - for us.
That doesn't mean that it wouldn't be for others.

Mary