Removing trees close to buildings

[matelot]

Tbh, my thoughts would be "what legal liability do you have to the homeowner?". If you've been asked to cut the tree down I can't see you having any liability if the house moves in ten years time. You also don't know what else will happen to the garden, that spot looks a good spot for a patio... A nice waterproof surface that is impervious to rain....

 

It looks a new house, I'd hope the foundations are relatively deep.

 

Amazing tree  has it not got a TPO?

[Will Heal]

Thanks for all of the replies.

I will go back to the home owner and tell them what could happen if they have it felled and suggest that they get a structural engineer to look at it.

If they still want to go ahead can I just get them to sign something to say that I cannot be held responsible if their house falls down afterwards?

 

The tree is in a conservation area and they have notified the council who have no problem with the tree being felled.

 

Yes it is a nice stick and milling it could be an option.

 

It's a bit ironic really- if it was further away from the building It wouldn't need to be felled but could be, but it's too close and it can't!

 

 

 

Thanks

 

Will

 

[beechwood]

Read this thread with interest.

Nearly 25 years in the industry and I've never seen a case of heave.
Read about, heard other people talk about it but never seen it.

To be honest I think it's a bit of the urban myth.
(I've said this to many people who look appalled but bear with me it's just my opinion, don't shoot me yet)

Here is why.

Most tree issues are logical and nothing beats logic and years of observations in the field.

Theoretically heave is possible but I take the view that it's a lot easier to take moisture out of clay than it is to put in back in.
Just let a lump of clay dry out and try it, you'd have to leave it sat in a bowl of water and for quite some time.

We did a huge amount of subsidence related work after the long hot summer of 2006.
All we did was fell and remove the offending trees for the insurance companies.
I asked the consultants at the time were the not worried about heave. There response was that heave was so rare that they advised the insurance companies to have the trees completely removed and deal with any heave if it became and issue later.

Obviously I don't know if any of these tree removals did result in heave but many of people we removed trees for the insurance companies have subsequently become clients and as I mentioned at the start I've never come across a case of heave.

I hate to think how many trees close to buildings, like the Yew Will looked at, I've felled and no one has ever come back to me complaining that their house has suffered heave as a result.

So my take on the question Will asked is to say.

I get asked the same question all the time and I respond by

Asking the client if they have had subsidence problems in the past?
Especially relating to 2006, as that was big surge year.

If they have
I explain about the theory of heave but say in my 25 years as an arborist I've never seen a case of it but theoretically it is a possibility so it's up to them.

I base this on the reasons I've listed above.

If they haven't
I explain about the theory of heave but say in my 25 years as an arborist I've never seen a case of it but theoretically it is a possibility but tell them that personally don't think it will be a problem.

I base this on the fact if there hasn't been any subsidence issues, it's unlikely that there house is built on a shrinkable clay sub soil and therefore heave is not going to be an issue.

That's my opinion.
I could be totally right or I could be totally wrong or the truth could be somewhere in the middle.

However Will suggestion of heavy reduction now any then felling it in a few years isn't a bad shout and he gets 2 jobs out of it.

Really interesting to get other people's take on it.
Have you ever seen a case of tree related heave?

Regards Neil

[Gary Prentice]

Have you read Giles Biddles book? 

 

Or the london court court case that Oisin Kelly was involved in? 

( Access to neighbouring land for pruning that would have caused heave then further subsidence if the pruning was continued regularly)

 

theres a difference between seasonal subsidence related to trees and the reaction involving a persistent moisture deficit.

Edited September 6, 2017 by Gary Prentice

[Gary Prentice]

Sorry Neil, my last post was on my phone and brevity leads to poor answers (in my case)

 

If a building is suffering from seasonal tree related subsidence, the soil beneath will be shrinking in the summer and the re-wetting/expanding when winter precipitation brings the moisture levels in the soil back up to somewhere near normal. Cracks will open in the summer and narrow in the winter. That's when most cases are identified and soil volume changes may be relatively minor.

 

On sites where there is a persistent soil moisture deficit (SMD) the underlying strata doesn't fully re-wet in the winter - partly for the reasons you've said and other reasons - the property may even be built on land that is already desiccated, so after tree removal and no further moisture extraction the soil, over time, expands fully and heave occurs. This can be dramatic and take years to fully rehydrate. I understand that in a lot of subsidence cases, where underpinning is necessary, ant-heave precautions are included in the construction to prevent further damage when significant expansion is predicted to occur. 

 

I don't know what experience/knowledge you have, so apologies if I'm teaching my grandmother to suck eggs , but it is a incredibly complex subject and all to often, because of costs and probabilities, trees are blamed on the balance of probabilities that they are the culprits.The loss adjusters want to settle the claim quickly and cheaply and maybe trees are removed when there are other causes such as settlement etc. 

 

I think I've only ever done tree work in half a dozen situations where there was subsidence, so no I've never been aware of heave after tree removal, but most of my working life has been up north on soils with very low PIs (Devensian tills, pennine coal measures and Kinderscoat sandstones in the main).

 

If you're interested researching further, Biddles book 'Tree root damage to buildings' is a must read ( but heavy going!) or the AA seminars on subsidence. 

 

[benedmonds]

On 06/09/2017 at 23:57, Gary Prentice said:

 

If you're interested researching further, Biddles book 'Tree root damage to buildings' is a must read ( but heavy going!) or the AA seminars on subsidence. 

 

Heavy going is an understatement...  Volume 2 is the most boring book I have ever tried to read...  

 

As others have said heave is very rare. As I understand it, It will only occur where a house is built on a dry soil with persistent soil moisture deficit. So the tree has to have been there before the house and the house built onto the dried soil.  The soil obviously needs to have a high plasticity index.

I think that the taking it down slowly over the years has been shown to be a waste of time (for the client) as if there is going to be swelling it will just happen over a longer time.

Also Having not suffered from seasonal subsidence is unlikely to have any bearing on the likelihood of heave.    

 

I recently spent a considerable amount of time trying to convince a client that his 5m prunus was not going to cause subsidence to his property. We reduced it and he is still concerned.. He now wants us back to remove it and I have spent even longer explaining why heave is equally unlikely...  I hate it when a client starts a sentence "I read on the internet"

Edited September 8, 2017 by benedmonds

[beechwood]

Sorry Neil, my last post was on my phone and brevity leads to poor answers (in my case)

 

If a building is suffering from seasonal tree related subsidence, the soil beneath will be shrinking in the summer and the re-wetting/expanding when winter precipitation brings the moisture levels in the soil back up to somewhere near normal. Cracks will open in the summer and narrow in the winter. That's when most cases are identified and soil volume changes may be relatively minor.

 

On sites where there is a persistent soil moisture deficit (SMD) the underlying strata doesn't fully re-wet in the winter - partly for the reasons you've said and other reasons - the property may even be built on land that is already desiccated, so after tree removal and no further moisture extraction the soil, over time, expands fully and heave occurs. This can be dramatic and take years to fully rehydrate. I understand that in a lot of subsidence cases, where underpinning is necessary, ant-heave precautions are included in the construction to prevent further damage when significant expansion is predicted to occur. 

 

I don't know what experience/knowledge you have, so apologies if I'm teaching my grandmother to suck eggs[emoji3] , but it is a incredibly complex subject and all to often, because of costs and probabilities, trees are blamed on the balance of probabilities that they are the culprits.The loss adjusters want to settle the claim quickly and cheaply and maybe trees are removed when there are other causes such as settlement etc. 

 

I think I've only ever done tree work in half a dozen situations where there was subsidence, so no I've never been aware of heave after tree removal, but most of my working life has been up north on soils with very low PIs (Devensian tills, pennine coal measures and Kinderscoat sandstones in the main).

 

If you're interested researching further, Biddles book 'Tree root damage to buildings' is a must read ( but heavy going!) or the AA seminars on subsidence. 

 

I did start to read Gile Biddles book a few years ago but lost the will quite quickly to be honest. Wasn't aware there was a second one.

 

Gary's I like your comments and agree it's a very complex subject.

In fairness my interactions with subsidence have by via removing trees for the loss adjusters/insurance companies and hadn't thought it might just be that the trees were getting blamed as it was quick/cheap way to settle a claim. But let's be honest the cynical side of me thinks it's very possible.

 

Even though no one else have come forward to saying they seen a case of heave following tree removal.

Obviously as you point out Giles Biddles book highlights cases and Paul mention one he was involved in.

I think I need to retract my 'heave is a urban myth' and replace it with 'heave is extremely rare'

 

Interesting posts, thanks fellas

 

Regards Neil

[daltontrees]

I wsa recently involved in a shrinkable clay tree case, pretty rare in Scotland, and although the generalites are complex enough when you have to apply them to real live cases it reminded me that it is very very diffcult to reach firm recommendations that stop short of excavating and exposing most of the foundations (at which point you may as well underpin while you're in there). There are never so many caveats in my other reports.

 

It strikes me that the OP's situation is as clear cut as it coud be that heave might occur if shrinkable clays are present. A tree that's probably more than a hundred years old, so it could be expected to have dried out any clays present thoroughly before the buiding appeared. A building that looks to me a  good bit younger than the tree. A building well within the zone of influence of a tree. A moderate water demand species that's maybe near it's full size. Looks like a bungalow, so quite a light structure.

 

The equation would seem to be this. If there are shrinkable clays with the worst kind of plasticity index, and if (taking account of the local climate and any persistent soil moisture defecits) the foundations of the house are in retrospect inadequate by current NJUG standards for that tree at that height and proximity, removal of the tree could cause heave.

 

Heave I agree is rare. But it does happen. Dried out clay will rehydrate, even if it takes years. And the force upwards might be small relative to the forces downwards in subsidence cases, but they could be significant, and if the structure is light it could be lifted.

 

But none of that is the original point. Should someone asked to remove a tree warn the owner? Morally, yes. Legally? Not so clear. But having asked for views on it on a public forum, in this case the answer has to be yes. Courts seem willing to take the view that tree contractors should have the expertise and duty to warn.

 

Removal in 2 phases is to my mind largely pointless. Saying heave is rare and probably not an issue is worse than saying nothing at all. I'd suggest to anyone asked if it's an issue, if you don't know don't advise. Better to say that you know enough to know that you don't know, and cover the situation in an informal communication (verbally with corroboration or in an email) that if in any doubt about the risk of heave the onwer should take specialist advice.   

 

 

[beechwood]

I wsa recently involved in a shrinkable clay tree case, pretty rare in Scotland, and although the generalites are complex enough when you have to apply them to real live cases it reminded me that it is very very diffcult to reach firm recommendations that stop short of excavating and exposing most of the foundations (at which point you may as well underpin while you're in there). There are never so many caveats in my other reports.
 
It strikes me that the OP's situation is as clear cut as it coud be that heave might occur if shrinkable clays are present. A tree that's probably more than a hundred years old, so it could be expected to have dried out any clays present thoroughly before the buiding appeared. A building that looks to me a  good bit younger than the tree. A building well within the zone of influence of a tree. A moderate water demand species that's maybe near it's full size. Looks like a bungalow, so quite a light structure.
 
The equation would seem to be this. If there are shrinkable clays with the worst kind of plasticity index, and if (taking account of the local climate and any persistent soil moisture defecits) the foundations of the house are in retrospect inadequate by current NJUG standards for that tree at that height and proximity, removal of the tree could cause heave.
 
Heave I agree is rare. But it does happen. Dried out clay will rehydrate, even if it takes years. And the force upwards might be small relative to the forces downwards in subsidence cases, but they could be significant, and if the structure is light it could be lifted.
 
But none of that is the original point. Should someone asked to remove a tree warn the owner? Morally, yes. Legally? Not so clear. But having asked for views on it on a public forum, in this case the answer has to be yes. Courts seem willing to take the view that tree contractors should have the expertise and duty to warn.
 
Removal in 2 phases is to my mind largely pointless. Saying heave is rare and probably not an issue is worse than saying nothing at all. I'd suggest to anyone asked if it's an issue, if you don't know don't advise. Better to say that you know enough to know that you don't know, and cover the situation in an informal communication (verbally with corroboration or in an email) that if in any doubt about the risk of heave the onwer should take specialist advice.   
 
 

Been away from this thread for a while but it's been playing on my mind and I see now that the felling of the original tree is going ahead.

Obviously our opinion differs but I'm genuinely interested in your view

So let's make it hypothetical.
I turn up to quote a job.
Mature tree 4m from clients house and well within the zone of influence of the species of tree (if I remember rightly their is a table in Giles Biddles book).
Tree is obviously older than the house.
Client wants the tree felled.
They tell me their garden is on clay soil.
They ask me 'will removing the tree cause any problems to our house'

I say, as you suggested, it's out of my area of expertise and that they need to seek advise from an appropriate expert.

I put them in touch with you, to produce a report for them.
How would it work?
I assume your proposed report would be sequence of elements, each one dependent on the outcome of the last.
If I am right in my assumption, what would the sequence of elements be and (roughly) how much would each cost ?

The other thing I'd like ask is
Reading your post the following question springs to mind.
If as you state 'it is very very difficult to reach firm recommendations that stop short of excavating and exposing most of the foundations' which is fairly obviously impracticable.'
If a client commissions a report will the client still not really get a straight answer, as the report will have so many caveats in it?

I'm not trying to pick holes in your post, I'm genuinely interested.

Regards Neil

[daltontrees]

If it were me the sequence of elements would be pretty much as I have already set out. Generalities of shrinkable clays. Effects on structures if shrinkage or expansion. How trees (or removal of them) affect soil moisture levels. How adequate foundation design can counter these. Then the facts. The tree, the distance, the conventional assumptions about water uptake of this tree. Then the unknowns. Foundation type and depth. Presence or absence of clay soils. Construction date and tree age. Then the recommendation, which would start with finding out if shrinkable clays are present locally. Finding out if records exist of foundation type and depth. And only then, possibly an excavation adjacent to the building to ascertain soil type and foundation type and depth and to a lesser extent an idea of root distribution. And only then would it be possible to say with any confidence whther the risk of heave is acceptable.

 

It is true there may never be a straight answer, but that's because it is impossible to see things uder the ground. An excavation is only a small random sample.

 

But what I don't know is whether if this advice was ignored, and the owner had the tree removed, and then experienced damaging heave of the building, and then claimed off insurance (possibly denying having taken advice), would the insurer pay out? By rights the answer should be no. But as I say I don't know, becasue I have no experience of this scenario. It may even depend on the wording of the insurance policy.

 

I can't say how much this would cost, I know what I would charge up here, but I'm not about to disclose my consultancy rates on a public forum.