Heave / subsidence from oak on clay soil

[joepatr]

Hi all

 

I’m based in North West London (an area with shrinkable clay subsoil) and currently have an oak tree in my garden, approx 6/7 metres tall. 

 

I’d like to have this taken down eventually but am obviously concerned about the risk of not only subsidence but also heave. 

 

Could anyone recommend the best way to manage this to ensure ensure the safety of my property? I was thinking the best way would be to have the tree slowly reduced over a period of time before having the stump totally removed. 

 

Would this be the way forward, if so, how much and over what period? I was thinking taking it down in quarters over the next few years but one of the local tree surgeons suggested thirds every couple of months. 

 

I’d be grateful for any suggestions and also any companies in the Hillingdon area who could help. 

[Rough Hewn]

Get the house underpinned.
Keep the tree.
[emoji3][emoji106][emoji106][emoji106]

[Rough Hewn]

That made me chuckle....  [emoji13]

"French pollard" at 3m
Mill the top half
Make a set of outdoor furniture
Build a pizza oven
Cut faggots every other year
With a saw on a stick
and keep the tree.
[emoji12][emoji23][emoji848][emoji106]

[Gary Prentice]

Staged reductions are no longer perceived to be  of any benefit (apart from to the tree surgeons bank account). 

 

There's lots of factors involved as to the risk of subsidence, or indeed heave, apart from tree, such as the age of the property and the distance of the tree from the property. 

[Squaredy]

1 hour ago, joepatr said:

Hi all

 

I’m based in North West London (an area with shrinkable clay subsoil) and currently have an oak tree in my garden, approx 6/7 metres tall. 

 

I’d like to have this taken down eventually but am obviously concerned about the risk of not only subsidence but also heave. 

 

Could anyone recommend the best way to manage this to ensure ensure the safety of my property? I was thinking the best way would be to have the tree slowly reduced over a period of time before having the stump totally removed. 

 

Would this be the way forward, if so, how much and over what period? I was thinking taking it down in quarters over the next few years but one of the local tree surgeons suggested thirds every couple of months. 

 

I’d be grateful for any suggestions and also any companies in the Hillingdon area who could help. 

A bit more detail about the house might help.  If it is modern with the correct footings it may well be a non issue.

[Mick Dempsey]

41 minutes ago, Gary Prentice said:

Staged reductions are no longer perceived to be  of any benefit (apart from to the tree surgeons bank account). 

 

There's lots of factors involved as to the risk of subsidence, or indeed heave, apart from tree, such as the age of the property and the distance of the tree from the property. 

Not that I’m wise after the event, I’m not wise at all really.

 

But I remember listening to the rationale behind staged removals at college and thinking it was nonsense.

[Mark Bolam]

It is Mick.

 

You need to involve a structural engineer with experience of these situations Joe.

[woody paul]

12 minutes ago, Mark Bolam said:

It is Mick.

 

You need to involve a structural engineer with experience of these situations Joe.

To right also you insurance company may need to informed or take there advice if they say anything just incase you have a problem in the future. 

[benedmonds]

12 minutes ago, Mark Bolam said:

You need to involve a structural engineer with experience of these situations Joe.

What is a structural engineer going tell you of any use?

It is a pretty small young tree, it is only going to get bigger so subsidence could become an issue..

As its a young tree it is unlikely to have caused a soil moisture deficit.

It is small therefore was probably not there before the house.  If it was there before the house then the house is newish and should have been built with sufficient foundations..  

There is nothing practical that I am aware of you can do to prevent any heave.

Remove the tree fix any damage..

[Mark Bolam]

Ben, we know nothing about the situation. We don’t even know if it’s a young tree.

A 6/7m tree could have a 5’ dia butt!

PI of soil?

Age of house?

Age of tree?

Type/depth of footings?

 

You’re right though, if it’s going to heave it’s going to heave.

[petercb]

If it heaves then it's not just the foundations potentially at risk, if it's a solid floor with no void underneath then floor could suffer from heave.

As mentioned much more detail needed. 

When building first part of our house in our woodland (clay soil) had long sessions with Building Control over depth and type of foundations due to surrounding trees none of which were above 9" dia at base nor particularly close.

 

Lots of useful info here;

 

https://www.labcwarranty.co.uk/blog/how-to-reduce-the-effects-of-ground-heave-following-tree-removal/

Edited January 24, 2019 by petercb