On Saturday, July 11, 2020 at 4:51:53 PM UTC-4, F Russell wrote:
On Sun, 12 Jul 2020 06:19:20 +1000, Rod Speed wrote:


Depends on why it has subsided like that.


The house was built on this suburban lot about 60 years
ago.

The subsidence has been very slow. In fact it is a not an
uncommon occurrence. Concrete driveways sometimes subside
and there are companies that offer a "pump it up" solution
as a cheaper alternative to replacement.

I'm not concerned about sinkholes. I just want to know
if exposing 12-18" of the top basement wall poses any
problem.

Sounds like it's a hole that's ugly and can fill with water. The ground
should be graded away from the house. Fill it in. I'd check where the
gutter water is going. Get out there in a heavy rain, you may find it's
not flowing where you think it is. I had water coming into a spot in
my basement, everything looked OK outside when it wasn't raining. Went
out in a heavy rain and realized water was backing up in one of those
corrogated pipes that was pulled up over a downspout, but not high enough.
Water was gushing out right at the foundation.