Eucalyptus blamed for Subsidence

[Rupe]

If you get to keep it, then you will have to fell it at some point in the not far off future. Get a silver birch instead and have an easy life.

[Ian Flatters]

TBH you need to look into the zone of influence and what plasticity index your soil is. Root pruning and root barriers may be an option but i imagine removal would be somewhat cheaper. . . Unfortunatly they are classed as high water demand species in nhbc chapter 4.2.

[Tony Croft aka hamadryad]

Plasticity index is the important thing, as are the foundation methods of construction.

 

i remember reading in "Has your house got cracks 2nd edition" that despite building research best advice to use pile and beam/raft style foundations in the pressence of shrinkable clays they still persist with the solid trench and strip style of foundations.

 

A eucs biology must be well adapted to manage its water content effectivley, it after all comes from a notoriously arrid region of the world. I have always thought that the eucs shallow rooting nature within the U.K (so many are leaners) is due to their lack of need to throw down deep roots here as needing so little being well adapted to the dry it finds more than sufficient moisture in the uper layers within our soggy climate.

 

has no one proposed an alternative solution? a root barrier and (albeit a costly affair) long term foliage managment/ and or irrigation of the tree?

 

like others though, its a euc!

[sean freeman]

It is unfortunate that the UK produces the same ridiculous classification systems for trees that we have here in some of our buidling standards..rather like the nonsense in that Canadian document...a scientific fact really requires some impirical evidence rather than a 'scientist' making a statement.

 

It is why the LTOA guidelines are (IMO) more useful and relevant.

[Tony Croft aka hamadryad]

It is unfortunate that the UK produces the same ridiculous classification systems for trees that we have here in some of our buidling standards..rather like the nonsense in that Canadian document...a scientific fact really requires some impirical evidence rather than a 'scientist' making a statement.

 

It is why the LTOA guidelines are (IMO) more useful and relevant.

 

I havent done a great deal of reading in this subject, a little but not enough to have an in depth view or appraisal of all the guidence, seems you know a lot about this subject sean, would love to hear what you have to say, maybe in a dedicated thread?

[Lee Winger]

Has anyone successfully defended an insurance case against a Euc? Or know a guy that has?

 

Mine is 14m from my house and the initial test pits have found only miniscule root hairs near the cracking, but my insurers are trying to pin it on suspect No 1. I've read a few of the past posts but most just say take the tree down.

 

Somebody mentioned guidelines in The Body Language of Trees? Will these help my cause.

 

The tree is about 25 years old and solid. I cannot bear to take it down. The soil is a clay type.

 

I need the Clint Eastwood of defending poor Eucs!

 

Many thanks in advance

 

S

 

Small shrubs have been known to cause subsidence in clay soils, let alone Eucalyptus, I've carried out loads of subsidence work, the NHBC planting guide is a good tool to work with if in doubt, trees and clay soils are a recipe for subsidence.

Edited November 30, 2010 by Lee Winger

[Albedo]

What I don't get is..... when an insurance company reckons a tree is causing subsidence on a clay soil, so recomends its removal.

 

If the claim of subsidence is real then wouldn't the removal of the tree almost by definition risk heave?

 

If the tree takes enough water from the (clay) soil to cause it to shrink, then the removal of the tree will cause it to expand the next time significant or prolonged rainfall occurs.

 

Also would like to see some evidence of a shrub being significant Lee. I bow to your experience but I am surprised by this.

 

 

just add as an edit : I would reckon that staged reduction and long term management would be the preferred option in this scenario

Edited November 30, 2010 by Albedo

[Lee Winger]

Plasticity index is the important thing, as are the foundation methods of construction.

 

You don't need a use a plasticity test for when you're sure you are dealing with London clay, records of seasonal fluctuation/dessication are good if times on your side, as for methods of construction only really relevant on houses built mid 80's onwards, treat all older buildings with extreme caution, well that's what I do

[sean freeman]

Tony I posted whilst you were typing you previous, however to address some of what you wrote and hopefully point towards why I feel so negatively towards the general advice regarding trees and subsidence...(Also of cousre I meant empirical not impirical...I blame my primary school teacher..nah just kidding lovely lady)

 

Eucalyptus is a huge and diverse genus with over 700 species, it is simply not true to try and argue that Eucs in general are adapted to arid conditions, they occur in the tropics, sub-tropics and temperate regions of our continent.

 

There is certainly validity (IMO) in your observation of the influence of the soil profile and moisture gradients in which trees have establuished and the architecture of the root system...however I would caution again about over generalising about the evolutionary factors at play in any one specific Eucalyptus sp.

 

i.e. You would not find many Australian Arbs trying to argue that E. camaldulensis or E. grandis are likely to have shallow roots in soil profiles with high moisture content.

 

Like all other tree species I can think of Eucs have evolved startegies to limit water losses during the hotest part of the day. They are remarkably similar to the other members of the Myrtaceae family in the way these have been expressed in the form and structure of their leaves.

 

There is (IMO) far more relevance in the site hydrology and geotechnical data (and as you alluded to Tony the building construction method!) than in the tree species when it comes to potential (or actual) subsidence impacts.

[Lee Winger]

What I don't get is..... when an insurance company reckons a tree is causing subsidence on a clay soil, so recomends its removal.

 

If the claim of subsidence is real then wouldn't the removal of the tree almost by definition risk heave?

 

No longer relevant in law, as even with a phased reduction the tree will extract the same amount of water as before the reduction, plus all living things die, you couldn't protect from heave, say if honey fungus struck and killed the tree, or it was hit by lightning.

 

When talking shrubs, I mean large laurels etc, even ivy and other climbers have caused subsidence, there was a case study where a row of trees were saved as it was proved beyond reasonable doubt, that it was shrubbery that caused the subsidence and not nearby trees