root protection barrier

[codlasher]

I installed a 2.1m root barrier recently using a 2.2m deep x .450 wide and 9.0m long trench. This was to protect a timber framed farm-house, built in approx 1641 from the roots of a mature willow tree. I used concrete and removed four 100mm roots that had already undermined the flank wall. We were originally going to a 3.0m depth but decided that as there were no signs of roots below the 2.2m depth the trench should stop there.

I'd not complain at a depth 1.5m as this will stop virtually all roots. I found the majority of roots from this willow to be in the first .500mm of soil. The owner of the property and I felt that we'd covered any future ground heave in going to this depth.

codlasher

Edited May 5, 2015 by codlasher

[Paul Melarange]

Is this a unreasonable request by the LA?

 

Not necessarily unreasonable, just unusual.

 

I would have thought that the building control officer would have specified a foundation type and depth that would have been sufficient without additional measures such as root barriers. However, I don't know the details of the project and I'm certainly not an engineer.

 

Is it a single storey extension or two?

 

The building control aspects of a planning consent are generally completely separate to the tree protection side of things (they can often provide conflicting advise/recommendations). It seems strange that a root barrier has been recommended to protect both the building and the tree.

 

Is the diameter of the stem (at 1.5m) less than or great than 67cm?

[Paul Melarange]

I installed a 2.1m root barrier recently using a 2.2m deep x .450 wide and 9.0m long trench. This was to protect a timber framed farm-house, built in approx 1641 from the roots of a mature willow tree. I used concrete and removed four 100mm roots that had already undermined the flank wall. We were originally going to a 3.0m depth but decided that as there were no signs of roots below the 2.2m depth the trench should stop there.

I'd not complain at a depth 1.5m as this will stop virtually all roots. I found the majority of roots from this willow to be in the first .500mm of soil. The owner of the property and I felt that we'd covered any future ground heave in going to this depth.

codlasher

 

That's really interesting Codlasher 👍

 

What type of soil was it? We're there any signs of damage to the structure of the building caused by tree?

 

Was the root barrier designed by an engineer? Or was it the home owner that came up with the idea?

[jaime bray]

It's an interesting topic. I remember reading somewhere about roots that are diverted away from structures with root barriers and such, will try and re direct they're orientation of growth back to the original position/direction of growth at point of contact with said barrier.

 

If you think about one of the fundamentals of roots this theory is viable. One requirements of roots is stabilisation. Roots orientate accordingly based on several factors, crown asymmetry/symmetry, favoured growing ; watery and nutrient, penetrable surface layers etc. So if a root is growing in a particular direction, and it's reason is stabilisation, then whilst elements of the re direction, will cause the root to bolster it's cell strength at weak points, re establishing it's original orientation and direction sounds like a good strategy for stabilisation and assistance in the trees desire to survive. This thought aligns with the principles of flow architecture and cell inter-linkage in woody plants.

 

Based on my interpretation...

 

So, to add my point, do root barriers, when installed, need to go way beyond the extent of the perceived foundation line or area of potential influence to reduce the propensity for the re direction to occur, thus resulting in the roots not influencing the foundations and zone of influence? The time frames of this is not a couple of years by the way. More medium to long term.

Edited May 5, 2015 by jaime bray

[codlasher]

That's really interesting Codlasher 👍

 

What type of soil was it? We're there any signs of damage to the structure of the building caused by tree?

 

Was the root barrier designed by an engineer? Or was it the home owner that came up with the idea?

 

Yes it was an interesting project. Made for some good thinking!

I'll answer your Q's in order; Good loam over heavy clay. Yes there was signs damage that is why I was called in as I have experience and machinery.

 

No engineer although I did put the Q on this forum. I did quite a lot of internet research on tree roots & root barriers. The property owner and I drew up a plan using what we knew of the local soil conditions whilst considering the best possible outcome for both the tree and the structure. I had trench-props and etc in case my soil sample had been wrong and we were digging on a midden! The owner had extensive knowlege of the properties structure as he'd taken it back to its bare shell some 20 years previously.

I found four roots (as I posted) and two were certainly under the flank wall resulting in heave by the weakest part which was the entrance door. This may settle or if not can be rectified by some remedial work.

 

I have been involved with similar projects in the past and there's one in Parktown, Oxford that I did 35 years ago on a brick arch structure. I visited this recently for the first time in a decade and it is still looking good.....I'll do the same with this as I like to keep long term notes:biggrin:

[tree79]

Yes it was an interesting project. Made for some good thinking!

I'll answer your Q's in order; Good loam over heavy clay. Yes there was signs damage that is why I was called in as I have experience and machinery.

 

No engineer although I did put the Q on this forum. I did quite a lot of internet research on tree roots & root barriers. The property owner and I drew up a plan using what we knew of the local soil conditions whilst considering the best possible outcome for both the tree and the structure. I had trench-props and etc in case my soil sample had been wrong and we were digging on a midden! The owner had extensive knowlege of the properties structure as he'd taken it back to its bare shell some 20 years previously.

I found four roots (as I posted) and two were certainly under the flank wall resulting in heave by the weakest part which was the entrance door. This may settle or if not can be rectified by some remedial work.

 

I have been involved with similar projects in the past and there's one in Parktown, Oxford that I did 35 years ago on a brick arch structure. I visited this recently for the first time in a decade and it is still looking good.....I'll do the same with this as I like to keep long term notes:biggrin:

 

 

 

Looks like an interesting project, and the fact the you revisited the one site and it still appears to fine is good know.