Trees on banks and retaining walls

[benedmonds]

I have come across this a few times but never really been happy with any solutions.  

What advice would you give to a client with a retaining wall being damaged by a tree.

Builders normally want to remove the trees so they can excavate rebuild.  

Others are will just remove the wall and cut any roots in the way.

 

In this case the tree is protected as is the wall... I am nervous that if the wall is removed stability could be compromised but not sure of any tried methods that others might have used.

[Rough Hewn]

I’ve got the same but in a CO.
Now they’ve slapped a TPO on it too.
My advice. Be prepared for a long battle with the council.[emoji22][emoji22][emoji22]

[benedmonds]

1 minute ago, Rough Hewn said:

I’ve got the same but in a CO.
Now they’ve slapped a TPO on it too.
My advice. Be prepared for a long battle with the council.

I don't want a battle, I want a practical engineering solution so the wall can be repaired without damaging the tree.

[doobin]

There isn’t one. It’s a conflict between two protected things. If you don’t cut the roots back they’ll keep pushing on the wall. You can’t build the wall further away cause it’s not the wall owners land. 
 

you could potentially airspade back and then build a secondary retaining wall that the tree can’t push over. Lots of work and mega money just because common sense can’t be applied by the council. 

Edited September 9, 2021 by doobin

[Rough Hewn]

I don't want a battle, I want a practical engineering solution so the wall can be repaired without damaging the tree.

As doobin says, there isn’t one.

[openspaceman]

1 hour ago, benedmonds said:

I don't want a battle, I want a practical engineering solution so the wall can be repaired without damaging the tree.

I cannot think of a solution other than sheet piling between the tree and wall but my concern would be that Heras fencing won't stop anything and walls falling have killed a few people in my recent recollection of reading the news.

 

The lime doesn't seem without issues either and no shortage of trees in the vicinity.

[daltontrees]

Arbtakk discussed this to death a couple of years ago. I recall my take was firstly to gauge how badly the client wants to keep the tree. This will establish whether it's a fight or a budget issue. Secondly if it's a fight, put an application in to remove (or possibly combined crown and root prune during a wall rebuild) and make it clear the tree is damaging the wall and will continue to do so. If refused, the Council will then become liable in compensation for further damage. You'd want a look at the possibility too of catastrophic failure, and if that's a reasonable possibility it might be defensible to undertake reduction based on the TPO risk exemption.

The rebuilding will depend on available space. A reinforced concrete wall will be a lot stronger per volume than masonry, so a replacement RC wall could be faced with stone slips cut from the existing wall.

It's going to come down to what is considered a reasonable hoop-jumping extent. The Council might not give a damn about expense but the courts don't say you have to go to any lengths to find an engineering solution. And if the Council's being unreasonable then appeal a refusal. An Inspector will probably (eventually) take a more pragmatic view.  Ideaslly then the parties will from the outset will anticipate a sensible appeal decision and won't make it have to go that far.

 

The pics suggest it's gone beyond doubt that removal of the wall would contribute quite soon to tree failure. The stones look pushed out so far that it's not just soil pressire, it's actual woody roots. Seriously limited options for cutting back the sorts of knuckles that cause that kind of deflection. The roots won't be needed for support unless htey're going straight downwards, but cuttign them in an aerated 'soil' environment with no room for callus will let in infection.  Wrong tree, wrong place.

 

How is the wall protected? Listed building?

 

Is htis in an area of shrinkable clays?

[dan blocker]

Exactly as Daltontrees says👍. This wall was unlikely to of been built that far out of plumb. As a rule of thumb if a wall is a third of its width out of vertical(or more) it should be considered potentially dangerous even without the cracks and dislodged walling stones? and should be surveyed and the fault rectified. It will have to be dismantled down to sound walling and rebuilt. The soil behind would have to be cut back as obviously work space is required.

Without knowing the wall thickness but taking a guess 🤔 it’s probably a combination of insufficient thickness, poor mortar, overloading of fill behind the wall and the tree🤭

A substantial RC wall with a facing would have to be probably thicker than existing and with little room to encroach onto what looks like a public pavement the tree will probably have to go😢. The tree won’t continue to flourish without the wall! As openspace says - if that wall fails the Heras fencing won’t stop Jack😳 Whoever has put this in place thinking it solves the problem is plain and simply wrong. Just a logical thought process as to what would happen if: (risk assessment )🤔would tell you that If the wall was to fail somebody could get seriously injured or worse! What if it was your children, grandchildren walking past? The council cannot refuse the tree removal once the run away train comes down the hill in their direction with the risk to the public safety down to them 😳.

[Dbikeguy]

The fact they have fenced it means they have admitted its dangerous, the loose walling needs removing asap or fence moving to allow for falling bricks not to push the Heras over as it’s the land owner liable when someone gets hurt.
I think its 100 tree removal and rebuild the wall, too close and too high up, anything planted there will in the future cause the same. Should be an easy win with the council for removal too as removal of the wall or replacement wouldn’t be in keeping with the area.

[kevinjohnsonmbe]

Just send the attached pic to the council!

 

Wall or tree?

 

The wall is a clear and present danger to public safety.

 

https://www.cornwalllive.com/news/cornwall-news/dangerous-looe-wall-forces-emergency-5628641