Sycamore tree with TPO

[eggsarascal]

3 hours ago, Gary Prentice said:

If the soil type is as stated (chalk) I think that tree related subsidence is rare or unusual.  But without onsite investigation it's unsafe to presume that is what is actually there. 

 

Are the cracks subject to seasonal changes? Are they uniform in width top to bottom or wider at the top - usual when a corner or side of the building subsides causing a rotational movement.  Cracks widening during the summer and closing up a little during the winter when (on shrinkable soils) the ground re-wets and expands? Another common indication is that doors and windows stick in the summer as the building rotates/twists but free up in the winter when the soil expands and the house rights itself a little. 

 

You're probably starting to realise tree related subsidence is a complex issue, which is why everyone is suggesting that you contact your insurers in the first instance. 

 

Cracks and damage o tarmac in that a proximity to the tree isn't unusual. The larger roots grow new cells around their circumference similar to the above ground parts and can create enough upward pressure to lift the overlying surfacing. It's fairly common and unlikely to provide sufficient reason to support an application to remove the tree if that was your desire, because there are engineering solutions available other than simply removing the tree.

 

Hope this helps a little.

What are the engineering work arounds Gary?, if that driveway was lifted by tree roots and the homeowner wanted to replace like for like, how would they go about it?

[Gary Prentice]

1 hour ago, eggsarascal said:

What are the engineering work arounds Gary?, if that driveway was lifted by tree roots and the homeowner wanted to replace like for like, how would they go about it?

Tree roots and hard surfaces are a continual problem everywhere. There's a lot of literature out there but essentially it seems that compromises have to be made and then any solution has to be site specific. 

 

Going off of the photo with a tree that's probably slowing in its growth rate the cheapest option would probably be just to lay a new wearing coat, accepting that there is the potential that some upheaval may occur again in future years.  There would be some argument that impermeable tarmac/asphalt would detrimental to the permeation of air and water, but the trees adapted to the existing surfacing so a fresh layer on top is, IMO, the least harmful solution. 

 

The next alternative I'd suggest would be the remove as much of the existing surface as practical (in accordance with the guidelines of BS5837 -the section on removing hard surfaces in RPAs) to lower the overall ground level before installing a cellular system like cellweb TRP. which can be surfaced with permeable tarmac to allow air/water to percolate down. Admittedly permeable asphalt/tarmac does tend to become less permeable in time IIRC. I'd debate with the LA TO that a normal tarmac wearing coat would only be replacing the existing surfacing (as long as everything was on the same footprint as the original drive) so wouldn't be detrimental. The problem with cellular systems is that surface levels are increased, so in circumstances where there are existing levels that the drive has to join such as the public footpath it isn't always feasible. 

 

The Americans use a lot of cast in situ concrete for footpaths which also has its pro's and cons. If it's agreed that the existing surfacing provides a non-permeable barrier within the RPA then carefully removing the upper tarmac layers (as above) and replacing with cast in situ concrete slabs, at least over the RPA, might be a solution.

 

Sorry Eggs, I don't think I've answered your question fully, but within the parameters of a like for like replacement these are what come to mind. A TO, who wanted to retain the tree, would probably say that rather than fell it gravel above the existing surface is sufficient - whether the homeowner liked it or not. Similarly, judges have decided that tree removal shouldn't be the first option before other solutions have been exhausted. 

 

I've had to take to a felling application to appeal after a refusal and demonstrate that there was no reasonable engineering solution because of the surrounding levels .e there was no alternative other than fell, although in that particular situation the damage was to a neighbours drive. I won the appeal but I'm still unsure how it would have gone if the damage had been to the owners drive - because of actionable nuisance the tree was causing.

 

Anyway, as a hypothetical question based on a blurry photo that's all I've got for now. If it was my house I'd probably skim over the top with more tarmac just to level it and accept it as a temporary short term solution. But I'd also work out, considering the surrounding levels, if cellweb was suitable as I believe it has a degree of flexibility that could, possibly/probably cope with future root expansion growth. Concrete slabs would be my least favourable solution, reading what I've read of the American experiences but hey, I'd at least consider it.

 

If anyone else cares to jump in with hypothetical engineering solutions feel free  

[daltontrees]

The spil type may not be relevant to subsidence, the underlying geology is. You can have loamy, chalky soils on shrinkable clays, although it's unlikely. COul dhte OP check the BGS site  http://mapapps.bgs.ac.uk/geologyofbritain3d/index.html

and tell us what the 'bedrock' gelology is?

[meaple]

Quote

The spil type may not be relevant to subsidence, the underlying geology is. You can have loamy, chalky soils on shrinkable clays, although it's unlikely. COul dhte OP check the BGS site  http://mapapps.bgs.ac.uk/geologyofbritain3d/index.html

and tell us what the 'bedrock' gelology is?

Superficial deposits: No superficial deposits recorded

Bedrock geology: Holywell Nodular Chalk Formation and New Pit Chalk Formation - Chalk. Sedimentary bedrock formed between 100.5 and 89.8 million years ago during the Cretaceous period.

Edited May 30, 2019 by meaple

[daltontrees]

19 minutes ago, meaple said:

Superficial deposits: No superficial deposits recorded

Bedrock geology: Holywell Nodular Chalk Formation and New Pit Chalk Formation - Chalk. Sedimentary bedrock formed between 100.5 and 89.8 million years ago during the Cretaceous period.

That's clear. No possibility whatsoever of subsidence.

 

I can't really add anything to Gary Prentice's suggestions, thye seem to be as much as you can do.

 

The damage to the building may be a result of setlement or shortcomings of building design or execution.

[kevinjohnsonmbe]

Inform / discuss / resolve via the insurance company is sound advice which is why it has been suggested by several.

 

The only caveat to that of course would be - is the tree known / declared within the insurance policy?

 

If there is a part of the policy qualifying questionnaire which asks about trees and proximity to the insured building and, either by accident or design, the information submitted by the policy holder was not entirely accurate, it could end up with an uninsured problem being brought to the attention of the insurer....

 

So I'd just add - check carefully the details of the insurance policy and then consider inform / discuss / resolve via insurance company.  

[meaple]

My insurance was sorted by mortgage broker and to my knowledge insurer was not asking about trees and proximity,  I'll check my policy before making any move. 

In situation that I need to make claim and it would be refused (ie. not disclosing that there is a tree -  but  insurer haven't ask about it in any forms) who is liable broker who was dealing with it,  property owner? What  would need to be done if something like this occurred? 

[eggsarascal]

19 hours ago, Gary Prentice said:

Tree roots and hard surfaces are a continual problem everywhere. There's a lot of literature out there but essentially it seems that compromises have to be made and then any solution has to be site specific. 

 

Going off of the photo with a tree that's probably slowing in its growth rate the cheapest option would probably be just to lay a new wearing coat, accepting that there is the potential that some upheaval may occur again in future years.  There would be some argument that impermeable tarmac/asphalt would detrimental to the permeation of air and water, but the trees adapted to the existing surfacing so a fresh layer on top is, IMO, the least harmful solution. 

 

The next alternative I'd suggest would be the remove as much of the existing surface as practical (in accordance with the guidelines of BS5837 -the section on removing hard surfaces in RPAs) to lower the overall ground level before installing a cellular system like cellweb TRP. which can be surfaced with permeable tarmac to allow air/water to percolate down. Admittedly permeable asphalt/tarmac does tend to become less permeable in time IIRC. I'd debate with the LA TO that a normal tarmac wearing coat would only be replacing the existing surfacing (as long as everything was on the same footprint as the original drive) so wouldn't be detrimental. The problem with cellular systems is that surface levels are increased, so in circumstances where there are existing levels that the drive has to join such as the public footpath it isn't always feasible. 

 

The Americans use a lot of cast in situ concrete for footpaths which also has its pro's and cons. If it's agreed that the existing surfacing provides a non-permeable barrier within the RPA then carefully removing the upper tarmac layers (as above) and replacing with cast in situ concrete slabs, at least over the RPA, might be a solution.

 

Sorry Eggs, I don't think I've answered your question fully, but within the parameters of a like for like replacement these are what come to mind. A TO, who wanted to retain the tree, would probably say that rather than fell it gravel above the existing surface is sufficient - whether the homeowner liked it or not. Similarly, judges have decided that tree removal shouldn't be the first option before other solutions have been exhausted. 

 

I've had to take to a felling application to appeal after a refusal and demonstrate that there was no reasonable engineering solution because of the surrounding levels .e there was no alternative other than fell, although in that particular situation the damage was to a neighbours drive. I won the appeal but I'm still unsure how it would have gone if the damage had been to the owners drive - because of actionable nuisance the tree was causing.

 

Anyway, as a hypothetical question based on a blurry photo that's all I've got for now. If it was my house I'd probably skim over the top with more tarmac just to level it and accept it as a temporary short term solution. But I'd also work out, considering the surrounding levels, if cellweb was suitable as I believe it has a degree of flexibility that could, possibly/probably cope with future root expansion growth. Concrete slabs would be my least favourable solution, reading what I've read of the American experiences but hey, I'd at least consider it.

 

If anyone else cares to jump in with hypothetical engineering solutions feel free  

Thanks Gary, more options than I imagined. I did suspect overlaying wearing course would be somewhere in the mix.

[Gary Prentice]

On 30/05/2019 at 20:08, eggsarascal said:

Thanks Gary, more options than I imagined. I did suspect overlaying wearing course would be somewhere in the mix.

And here's another one for vehicles up to 3 ton which only raises the ground level by 85mm

 

https://greengridsystems.com/root-bridge-variants/light-15kn

 

I'm not conversant with it, the system has been discussed on another forum today.