DIYbanter - View Single Post

wrote:

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.

Well, accordng to teh guys who did soil tests and advised on foundatns
or here, what happens is that teh tree roots permeate teh soil, and
lower the local water content, causing long term shrinkage.

If youi remove the tree, or cut the roots, the water content returns to
normal.

In order to satbilise my house, they isnisted teh foiundations go below
teh level at which they ad found root hairs, and also insisetd that teh
foundations be lined with polystyrene to abosrb any heave, and that
tehfloors be suspended conctere for the same reason,. the raionale being
that as the cut roots died, the soil would expand again slowly.

It would seem to me that a concrete underground wall going down below
tree root level, would essentially place the tree in a 'pot' that would
stop its roots drying out that part of the soil under the house, and
immediately adjacent to it.

Of course teh attendant heave would result thereafter...

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.

Good. In the end, we may simply do nothing, other than cosmetic
patching, and pay extra insurance...and use that to get a price reduction..

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.

Thanks. I take that point well.

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

It is when you borow money against...the property. Its a condition of
lending.

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.

We shall see.

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.

This is not a cash buty - its part of a business plan doen on all
borrowed money. The option to have a total loss of the structure is not
something the bank would contenmplate.

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.

Yes, but they don't e.g lower the water table in outer mongolia when
growing in milton keynes.

The important thing is to prevent localised lowering in the vicinity of
the structure. Keeping the roots from appraching closer than about 6
feet is probably good enough.

Its obviously useless on new builds - why no make the foundations that
deep anyway? - but may have merit as a remedial action. I'll see what
structural engineers have to say.

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.

Yes. The question is how far and how fast.

The more I think about it the more I keep comong back to those trees.

Maybe they will have to go and thats that.

NT