"The Natural Philosopher" wrote in message
...
Been looking at a poetntial buy for a friend, and it looks like part
of
it - a rather shoddy 70's extension - has a bit of a subsidence
problem.
Possibly due to a couple of trees nearby - one a willow.

IF - and pending investigation - it needs underpinning, has anyone
any
ball park estimates for costs?

Walking away from the buy is not in the frame really - its more
about
price adjustment to reflect the condition.


Relevant information is :-

- access for machinery is no problem
- it's on clay soil, and wettish clay (quite low lying)
- about 20 meters of wall might need treatment.
- my guess is there are minimal foundations - one or two feet at the
very most.

My wet finger guesstimate was a grand a meter absolute tops,
thinking
that it could hardly take more than a week for a bloke with a shovel
and
a cement mixer to dig out a bit and fill it with concrete. At 10
quid a
day max.

It could be possible to take up the internal floors as well if this
is
desirable, but that would be far more of a job.

I am after any information anyone has on techniques that are
employed to
do this job, and any real world data that is better than my wet
finger
guesstimates.

In fact any information on mild subsidence and its remedy would be
welcome.

I seem to recall a test case (?? in Wimbeldon??) where if the work was
done on the extension when it was built under normal planning and
building regs control the local authority picked up liability as they
had charged for inspections. It was following that case that local
authoities increased the required depths of foundations markedly.

AWEM