The natural philospoher:

What might be very simple and totally possible is to trench down a
couple of meters about a foot from the footings, and fill that with
concrete. That would cut the roots there, and stop any further
penetration to the footings area. I believe willow roots are pretty
shallow.

I dont see how that would make any difference. In fact it might
possibly cause extra problems.


Of course doing that UNDER the footings and backfilling with concrete
and mortar would be ideal..

yes


Any property in sound structural condition can be insured if you take
insurance that specifically excludes subsidence. There are specialist
insurers that take on these kind of risks.

Any property suffering from undiagnosed untreated subsidence will not
get insurance, at least not without deception, which would render the
policy invalid anyway. So its pointless phoning around. The only
company to ask if the existing insurer, who might be prepared to
continue insuring - although at several times the price, and, be aware
of this, any fault that existed when you bought woulod be automatically
exlcuded from insurance. Of course they might not mention that to you.

Do realise that house insurance is optional. Of course its desirable,
but I would not assume that it was automatically essential.

If you get the present owner to make an insurance claim, they would
hopefully fix it all up for you, minus the excess. Unfortunately this
will seriously blight the property value, insurability and sale value.


I totally agree that an uninsurable property is worth only plot value

less clearance costs.

This isnt at all realistic imho. There are loads of uninsurable
properties that function as houses just fine. Mortgage cos will
absolutely not lend on such houses, dramatically cutting the field of
potential buyers. Sale value may be a few tens of k less.


My gut instinct is to go deep alongside, and pour some concrete to
prevent the roots getting back in.

I really doubt it would make any difference. Understand the problem:
trees cause changes in water levels, which cause shrink or expansion in
clay soils. It is this that cracks houses.



That is a possible and very attractive option, since we know that
extension has been up for years, and isn't falling down...its just
caused some noticeable cracking - up to 6mm in places.

6mm is not large. If its not currently moving you could probably just
glue it together at the cracks and leave it at that, although of course
it is your surveyors advice you should follow, I'm certainly not trying
to supplant that. If it is moving, things would be different, and
probably a lot more expensive.


NT