Insurance companies and trees

[Mark Bolam]

My mates have a subsidence issue with their house.

2 years ago their insurance company insisted that was due to their neighbours mature oak tree (TPO’d), and insisted on a 1.5m crown reduction, which was granted and carried out.

The insurance company have done trial pits and soil tests (clay).

 

The house is still cracking.

 

They have now shifted the blame to the mature leyland cypress at the end of their drive. This tree is a maiden, and actually looks pretty good. Classic standalone form, probably 22m.

Both trees are about 15m away from their house.

 

The latest request, based on an arb report, is to reduce the cypress to 16m, and cut back extended laterals.

 

Can anyone (with a bit of knowledge) explain to me exactly what this is meant to achieve?

 

 

[Stubby]

On 05/10/2023 at 19:31, Mark Bolam said:

My mates have a subsidence issue with their house.

2 years ago their insurance company insisted that was due to their neighbours mature oak tree (TPO’d), and insisted on a 1.5m crown reduction, which was granted and carried out.

The insurance company have done trial pits and soil tests (clay).

 

The house is still cracking.

 

They have now shifted the blame to the mature leyland cypress at the end of their drive. This tree is a maiden, and actually looks pretty good. Classic standalone form, probably 22m.

Both trees are about 15m away from their house.

 

The latest request, based on an arb report, is to reduce the cypress to 16m, and cut back extended laterals.

 

Can anyone (with a bit of knowledge) explain to me exactly what this is meant to achieve?

 

 

As far as I can tell Mark nothing other than bugger the form . Roots are still there . 

[maybelateron]

I assume the idea is that by reducing the amount of foliage/size of tree you are reducing the amount of water drawn out of the clay soil. This then allows the clay to expand a little, rather than continue shrinking, and making subsidence worse.

 

Or am I talking nonsense?

[Dan Maynard]

Low cost option for the insurance company to make it look so crap the owners pay to have it removed.

 

I don't get the idea really that you can just balance the amount of tree to give just the right amount of water extraction from the ground to halt subsidence. Last few years have been really really dry, subsidence claims have rocketed. 

[Andrew McEwan]

Is it just a classic speculative arb subs report, or is it based on known tree related movement? Spec-ing a nibble at the leylandii sounds like guessing is happening to me. I'd want to see cyclical crack monitoring data and live root id from their trial pits before any saws came out, even if they have proved the building is on a highly shrinkable clay. Often the arb subs report I see are little better than an educated guess that trees are involved, as it's way cheaper to have a stab at ruling the trees out first, rather than figuring out what is actually causing damage. If the cracks aren't opening and closing in line with the seasons then not likely vegetation is causing damage. I'd also want to know about any drainage issue that could be flushing fines out from under foundations, or differential settlement between a new extension or bay window etc on shallow foundations.

[Clutchy]

We do subsidence claims/surveys and then the work every day at the moment as last year was such an event year. Without seeing the site, my guess is the Oak should of been felled rather than reduced. 

 

It's almost always the Oaks that are the culprit out of the 100's jobs I've seen. 

 

Leylandii is also fairly common, but normally only stems within 8m of damage tend to get removed. 

[Clutchy]

21 hours ago, Andrew McEwan said:

Is it just a classic speculative arb subs report, or is it based on known tree related movement? Spec-ing a nibble at the leylandii sounds like guessing is happening to me. I'd want to see cyclical crack monitoring data and live root id from their trial pits before any saws came out, even if they have proved the building is on a highly shrinkable clay. Often the arb subs report I see are little better than an educated guess that trees are involved, as it's way cheaper to have a stab at ruling the trees out first, rather than figuring out what is actually causing damage. If the cracks aren't opening and closing in line with the seasons then not likely vegetation is causing damage. I'd also want to know about any drainage issue that could be flushing fines out from under foundations, or differential settlement between a new extension or bay window etc on shallow foundations.

 

 

Its so frustrating. We recently were instructed to remove 2 mature Beech trees that had been in situ with the house for over 80 years and predated the house by another 50 years.

 

An old coal door that was sealed up 30 years prior has started to show cracking where it was bricked up and rendered. No other damage, no crack monitoring, no SI, no root testing. 

 

It's so annoying that the default is to fell nearby trees 

[Mark Bolam]

On 07/10/2023 at 09:14, maybelateron said:

I assume the idea is that by reducing the amount of foliage/size of tree you are reducing the amount of water drawn out of the clay soil. This then allows the clay to expand a little, rather than continue shrinking, and making subsidence worse.

 

Or am I talking nonsense?

That’s the theory I suppose, but will it work?

It’s been dry here for ages, but will probably start pissing down soon until about April.

 

I should see the report this week.

[Dan Maynard]

58 minutes ago, Mark Bolam said:

That’s the theory I suppose, but will it work?

It’s been dry here for ages, but will probably start pissing down soon until about April.

That's what I mean, can't see it working. The rain isn't constant, and nor is the water demand of a tree.

[daltontrees]

Something similar to this came up on another group (British Tree officers and Tree Consultants). The consensus was (and backed by plenty of published studies) that crown reduction has to be very very substantial before it willl reduce water uptake. Talking over 50%, closer to 70%. And the effect would only be temporary.  

 

So I don't know what the 6m height reduction is expected to achieve, but if it's a reduction in shrinkage it wont. Maybe if it's done every year till the end of time it might make a significant difference. Proving or disproving it would be almost impossible