Frank Watson wrote:

On Sun, 17 Aug 2003 08:32:48 +0100, Tony Williams
wrote:



I'd think twice about a house with a solid evergreen
hedge..... the amount of labour, does it need ladders
to cut, and (most important) how much sunlight does
it block off the garden in winter.


Tony, That's an interesting comment; thanks for it.. Actually, my
hedge is only about 20 ft long, so I doubt if it would deter anyone
from buying the house. (They could easily have the hedge cut down if
they can't hack the prospect of keeping it trimmed).

I'm still hoping someone with experience of the following will offer
some info into how much of a threat the hedge is to my house's
foundations - especially if I cut it down, and the roots rot away.
Does anyone know how far Leylandii roots spread, radially, outwards
from the trunk?



They are not the worst by a LONG chalk.

Deep diving tap roots are not so much an issue as wide spreading roots
near the surface. I believe that Ash, and Willow are the two worst in
this respect. Certainly willow roots will travel as far wide as the tree
is tall - and anecdotally further. Ash is also bad news allegedly. When
I bult my house adjacaent (3m) to some trees- ash, maple, and indeed a
short stretch of very well hacked about Leylandii, they made me go down
nearly 3m on that bit of the foundation. OTOH I have other trees that
are further way, that they really didn't fuss about too much. The ASH
tree had definitely lifted the old pathway that used to run down the
side, and there is a local road with a ridge running across it that
points directly at another ash tree. That road is about 10foot wide with
teh teree in a hedge...somewaht above the road.

Frankly, for small leylandii, I'd gues at 3m being fine. If you let it
go to redwood dimensions, I'd double that. But not much more. They don't
go both far AND deep, and therefore will stop at teh wall foundations.
Its the nes that go deep and wide - the ash and willow - that are teh
real problems.

Building regulations give the following guidelines for

(a) Poplars, elms or willows;
The foundations should be 1.5m for a distance aay equal to the height of
the mature tree, up to 2.8m deep if closer than 1/4 mature height.
These are teh ones that suck moisture really hard.

(b) Other trees, foundations 1m-2.4meters for distances between 1, and
one quarter of the mature height.

(c) If near a bank of trees, increase depths by up to 50%

In no case do they talk about being closer than 1/4 the mature height,
and so that should presumably be regarded as a safe limit.

The regs. also say that 'building on shallow foundations should be more
than 1.5 tims the tree height away from it, or if a bank of trees, twice
the height away' (paraphrased for brevity)

So that is the gude to erecting NEW structuires near trees. Needless to
say its written to more or less guarantee no problems with any tree on
any soil with any acceptable foundation quality. Its mainy there to
adress issues of curtting foundations through tree rooots, which leads
to localised increased levels of water as the tree roots die, and
subsequent heave.

It doesn't say what the issues are in the case of planting trees near an
existing foundation.

My *guess* is, that the real issues are

(i) If the tree roots run *to* the foundations, they will swell
themselves, and also dehydrate the soil on the outside of the wall. This
may affect paths, but not necessarily the foundations, tho some
*sideways* pressure will be inevitable. You can possibly alleviate this
by trenching around teh foundations and back filling with gravel or
whatebver to abosrb movement on the outside soil.

(ii) If they run UNDER the fundations, you are in potentially very bad
trouble indeed. They may easily lift sections, or collapse sections,
according to the root swell/dehyrdation factor as to whether its
subsidence or heave. When I originally nought my house, the insurance
company stipulated that I must keep the nearby trees lopped, which I
never did - I just knocked the house down in the end and rebuilt to the
regulations. But it does give an indication that unchecked tree growth
beside a house is actuarily significant enough for it to be an insurance
issue.

Corection for this kind of problem would inolve trenching, root cutting
and underpinning to a significant depth, so I'd say look long and hard
at letting trees reach significant size near a house. AND the remedial
work is likely to render a blow-over in a gale more likely too.

Having said all of that - as general dumping of accumulated scraps of
knowledge and experience. I did have a fairly tall leylandii about 8
foot from one corner of the old house, that had a bole about 18 inches
across and was about 10 m tall. Not that old. I cut tha down, and burned
out the stump by simply lighting fires on it untill it was enough below
soil to cover over (lovely crops of wood eating fungi for years afterwards)

When we demolsihed te house, that corner, despite having foundations
that seemed to consist of three rows of bricks laid straight onto wet
clay :-) were in no worse shape than the rest of the house.

So in PRACTICAL terms, if you are triming your leylandii below riudge
height, and they are better than 3m away, I don't think they will cause
you much real trouble. OTOH any surveyor who sees em is going to putrse
his lips in that peculiar way, and teh incoming residents insurance
company is going to want to see them removed or lopped, or possibly ebne
refuse insurance, so the potential reslae value of the house will not be
good. Moral is to remove them well before you sell, so that all traces
are gone, and teh actual decay of the roots hasn't caused visible
problems yet. Say 2 years :-)

Or, if you just want to play safe, no trees of a heght greater than
their distance from the house should be allowed to grow.

Period.







Thanks

Frank