Tim Lamb wrote:
In article , Huge
writes
Not oak, no. Main problems I have seen are willows and ash.
Oak trees are nearly as bad as willows when it comes to subsidence caused by the
water they transpire. The nearest an oak should be to your house is 1.5 times
the drip line (IOW, 1.5 times the radius of the canopy).

I wouldn't worry about the water pipe, though.

Point of order, Huge.

Does this rule apply where the subsoil is river gravel with a highish
(3'0") water table?

I am about to re-build a farm toilet and am reluctant to destroy the
Leylandi screen.


When I did my house, Tim, the BCO insisted on soil samples to make sure
that the base of the footings were well below 'tree root hair' level.

Since there was a pretty mature ash and maple tree right there, this
ended up as about 2.2meters, and the digger over cut them to 2.5...

We also were required to line the footings with crushable foam sheet. So
that heave would be absorbed where we had cut through the roots.

ISTR you have a digger..the answer is, go deep. Leylandii are
particularly shallow rooted, and they do very little below about
0.5meters. If the soil is ultra soggy, they will not have an incentive
to go deeper either.

Frankly if you re in the least bit worried, check with BCO, but I would
say a 1-1.5 meter trench full of concrete would be absolutely more than
adequate to deal with any issues arising.

In essence, even in the ground gets dried up by the roots and shrinks,
as long as the base of the footings are in the wet bit, you are
essentially safe from downward movements, and if you lay a few bits of
rebar in as well, it won't crack out sideways either.


The full monty of all foundations is to go about 2.5 meters down either
with piles or a slit trench, and use rebar.

You can pretty much plant a willow alongside that and it will simply hit
that. and turn round and run in the other direction. It can't undermine
it.they just don't GO that deep. Not much really does, except in very
dry soils..

If uou are paranoid as my BCO was, you pin (use lengths of rebar driven
in sideways)slabs of polystyrene foam to the trench walls before
pouring. Its cheap, and makes a gap between te soil and the footings..

I was a a bit aghast at all this, but then I worked out the costs, and
for a few hundred I got total peace of mind. Worth it.





regards