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. 

[Mark J]

If it was my tree, I'd be inclined to reduce it by maybe 15-20 percent and keep it about that size by pruning every few years.  My reasoning being: if it hasn't caused an episode of subsidence at its current size, a reduction may be significant enough to prevent it from doing so in the future.

That way, heave isn't very much of a consideration, the risk of subsidence is lowered, you get more light and the tree gets to stay.
It's not my tree though and I know nothing of the site or its history, but it may be an avenue worth exploring.

 

 

Edited January 25, 2019 by Mark J

[Mark Bolam]

Hadaway with your sensible comments Mark.

We had a good argument building here.

[Mark J]

31 minutes ago, Mark Bolam said:

Hadaway with your sensible comments Mark.

We had a good argument building here.

Sorry. I meant, fell the house and set fire to the tree. Or he could just move house and let someone else deal with it.

Edited January 25, 2019 by Mark J

[Khriss]

Will reiterate, get structural engineers report on yr house / foundations / soil type and drainage, the Arb report on tree and it's future . Without information, it's just as long as this thread. Because banks decided to include subsidence insurance in their loan policy, thousands of spurious claims with thousands of trees un-necessarily pruned or removed have occured. This isnt the case on the continent. They put up with a few cracks. K

 

[Boo Who?]

If it was my tree, I'd be inclined to reduce it by maybe 15-20 percent and keep it about that size by pruning every few years.  My reasoning being: if it hasn't caused an episode of subsidence at its current size, a reduction may be significant enough to prevent it from doing so in the future.
That way, heave isn't very much of a consideration, the risk of subsidence is lowered, you get more light and the tree gets to stay.
It's not my tree though and I know nothing of the site or its history, but it may be an avenue worth exploring.
 
 

I thought reducing a tree reduces leaf cover short term, but ultimately leads to a larger leaf mass in a shorter period of time than thinning or leaving a tree alone. So I’d say thin the tree suitably to reduce leaf cover and then maintain that. That way not altering the external aspect of the tree and actually reducing the foliage cover for a longer period of time than reducing it.
I can’t remember where I read this so don’t know who’s theory it is, but I am sure someone else can corroborate this...

[Mark J]

3 minutes ago, Boo Who? said:

I thought reducing a tree reduces leaf cover short term, but ultimately leads to a larger leaf mass in a shorter period of time than thinning or leaving a tree alone. So I’d say thin the tree suitably to reduce leaf cover and then maintain that. That way not altering the external aspect of the tree and actually reducing the foliage cover for a longer period of time than reducing it.
I can’t remember where I read this so don’t know who’s theory it is, but I am sure someone else can corroborate this...

I get where you're coming from. I'm of the opinion that well executed reductions don't lead to panic flushing.

[Boo Who?]

I get where you're coming from. I'm of the opinion that well executed reductions don't lead to panic flushing.

I agree, however even the best intended lead shoot that is left will ultimately be chased up by at least one, if not two or more adventitious buds that all produce more leaf cover. More than if it had just been left to grow on in the first place.

[Mark J]

Just now, Boo Who? said:

I agree, however even the best intended lead shoot that is left will ultimately be chased up by at least one, if not two or more adventitious buds that all produce more leaf cover. More than if it had just been left to grow on in the first place.

I'm not usually a fan of recommending reductions for the reasons you mention. In this case though I think it would be a more successful method of ensuring the longevity of the tree.

What happens when the tree grows again to the point where the moisture abstraction is posing a substantial risk of subsidence? Keep thinning it?

[Boo Who?]

I'm not usually a fan of recommending reductions for the reasons you mention. In this case though I think it would be a more successful method of ensuring the longevity of the tree.

What happens when the tree grows again to the point where the moisture abstraction is posing a substantial risk of subsidence? Keep thinning it?

No that is when you then move on to reducing the tree. A thin should leave a suitable structure for a later reduction according to recommendations. I believe a reduction should be the last resort as it ultimately changes the visual aspect of the tree forever and believe we shouldn’t interfere as much as we do

 

Customers always right though... so reduce a lot more trees than I want to!

[Mark J]

1 minute ago, Boo Who? said:

No that is when you then move on to reducing the tree. A thin should leave a suitable structure for a later reduction according to recommendations. I believe a reduction should be the last resort as it ultimately changes the visual aspect of the tree forever and believe we shouldn’t interfere as much as we do

I suppose you could approach it a number of ways. I'm with you on not interfering so much. Sometimes though we're left with no choice due to people building houses right next to trees.