What is considered the RPZ for a tree with a TPO?

[daltontrees]

1 hour ago, monkeybusiness said:

So it can no longer be offset? I’m pretty sure with justification it can, and 20% is  still a good rule of thumb to go by.

Yes with justification. But see my previous post, a 20% shift is only 5% of the RPA area. Why 20%?

Edited December 11, 2021 by daltontrees

[daltontrees]

1 hour ago, Khriss said:

Would also agree there, on offsetting if soil or structure conditions allow  . Plus shed on sleepers so its not a bad result for the tree . Currently converting a contractor to BS3998  -2010 , so there is a long way to go K 

Yes, but I wouldn't agree on your reasons, Yes if tolerance to damage allows, and/or yes if existing features indicate that it has happened naturally.

[Chris at eden]

23 hours ago, monkeybusiness said:

So it can no longer be offset? I’m pretty sure with justification it can, and 20% is  still a good rule of thumb to go by.

The RPA can be amended with justification but the 20% bit isn’t relevant.  I used to be the you could just do it but some people were offsetting RPAs in the direction of roads or other areas where there would clearly be no roots and then building right up to the RPA on the reduced side. In that instance it would be a reduction in the a RPA. 

When you now amend the RPA it’s to reflect ground conditions, so to move it away from a road or building. You can’t just offset it and say it will be fine and the tree can tolerate it just to get a building in.  It has to be with the trees benefit in mind, not the building. 
 

Sometimes if I get an app where the building is say 5% into an RPA I will say the impact will be low as the lost roots can be replaced on the other sides.  I would show it as an incursion and then recommend mitigation by hand digging and root pruning under supervision.   More often than not that will be accepted. I would never try to hide it as an offset and just say no impact and I wouldn’t try it with a 20% incursion.  In that instance I would recommend re-siting or engineering solutions. 

Cheers 

 

chris

 

[monkeybusiness]

2 hours ago, Chris at eden said:

The RPA can be amended with justification but the 20% bit isn’t relevant.  I used to be the you could just do it but some people were offsetting RPAs in the direction of roads or other areas where there would clearly be no roots and then building right up to the RPA on the reduced side. In that instance it would be a reduction in the a RPA. 

When you now amend the RPA it’s to reflect ground conditions, so to move it away from a road or building. You can’t just offset it and say it will be fine and the tree can tolerate it just to get a building in.  It has to be with the trees benefit in mind, not the building. 
 

Sometimes if I get an app where the building is say 5% into an RPA I will say the impact will be low as the lost roots can be replaced on the other sides.  I would show it as an incursion and then recommend mitigation by hand digging and root pruning under supervision.   More often than not that will be accepted. I would never try to hide it as an offset and just say no impact and I wouldn’t try it with a 20% incursion.  In that instance I would recommend re-siting or engineering solutions. 

Cheers 

 

chris

 

My understanding of the offset was (and still is) that it was always (2005 regs) only available where ground conditions allow (hence my bracketed ‘depending on ground conditions’ caveat). 

 

As a basic ‘turn up to quote/bounce ideas off a customer/see if there is any realistic chance of a proposal working’ and not go to the initial expense of an arboricultural consultant being employed to measure up/justify their fee/tell you ‘computer-says-no’… then 12x stem diameter and 20% offset is a good rule of thumb (as per my original post) (even though pedants will point out that there are many many more words and punctuation marks in the current guidance). 

 

Edited December 12, 2021 by monkeybusiness

[daltontrees]

I'm probably that pedant. But if you think I'm bad, some of the TOs around here will fight you to appeal on a comma. The best interpretation of the Standard is what the Standard actually says, so for me no 'rule' is needed, just justification. Although fair enough at the talkings-sake stage I might tell a client 20% could be justifiable with care. Last week I justified 90% because the tree was beside a 150 year old  railway bridge pillar with 12 foot deep foundations. Last month in the same area the TO would not accept 5%. He's used to people getting given leeway and then taking the piss.

 

[dan blocker]

RPA and CEZs aside and purely from an observer point of view - by covering an area under the tree with a cabin and a shed even with out excavations for foundations are you not creating a large area under the tree that is impervious to rain water. Surely that isn’t acceptable for the long term health of the tree🤔. Even with down pipes discharging onto the surface of the ground.

[daltontrees]

On 13/12/2021 at 19:45, dan blocker said:

RPA and CEZs aside and purely from an observer point of view - by covering an area under the tree with a cabin and a shed even with out excavations for foundations are you not creating a large area under the tree that is impervious to rain water. Surely that isn’t acceptable for the long term health of the tree🤔. Even with down pipes discharging onto the surface of the ground.

Water will go sideways to some extent. Not ideal but bearable if small.

I am just back in form a job, two mature hawthorns almost identical in size almost beside each other. One has a plastic shed about 6' x 6' right beside it and has about 50% crown dieback. The other has nothing over its roots and has 0% crown dieback. The only difference is the shed.

[Chris at eden]

On 12/12/2021 at 13:36, monkeybusiness said:

My understanding of the offset was (and still is) that it was always (2005 regs) only available where ground conditions allow (hence my bracketed ‘depending on ground conditions’ caveat). 

 

As a basic ‘turn up to quote/bounce ideas off a customer/see if there is any realistic chance of a proposal working’ and not go to the initial expense of an arboricultural consultant being employed to measure up/justify their fee/tell you ‘computer-says-no’… then 12x stem diameter and 20% offset is a good rule of thumb (as per my original post) (even though pedants will point out that there are many many more words and punctuation marks in the current guidance). 

 

It’s been a long time since I looked at the 2005 standard but from memory I think you could just do the 20% offset irrespective of ground conditions.  Could be wrong, I have slept over 3000 times since I last read it. 
 

Arb consultants don’t do the computers says no approach, or at least they shouldn’t. They should be doing a site specific assessment and then trying to resolve any issues that arise.  
 

As I said before the 20% offset is not relevant.  If it was it wouldn’t have been deleted from the current standard. I have sat on dozens of planning appeals as both a TO and consultant and if you start banding around incorrect info like the 20% offset the other side is going to point out that it was deleted for a reason and you will lose credibility with the planning inspector.  The first PINS appeal I sat on about 12 years was against a TRN. The inspector ended up telling the appellant to be quiet and accept the free advice she being given and she kept coming up with nonsense off the internet that was really easy to discredit.  
 

 

[daltontrees]

53 minutes ago, Chris at eden said:

It’s been a long time since I looked at the 2005 standard but from memory I think you could just do the 20% offset irrespective of ground conditions.  Could be wrong, I have slept over 3000 times since I last read it. 
 

Arb consultants don’t do the computers says no approach, or at least they shouldn’t. They should be doing a site specific assessment and then trying to resolve any issues that arise.  
 

As I said before the 20% offset is not relevant.  If it was it wouldn’t have been deleted from the current standard. I have sat on dozens of planning appeals as both a TO and consultant and if you start banding around incorrect info like the 20% offset the other side is going to point out that it was deleted for a reason and you will lose credibility with the planning inspector.  The first PINS appeal I sat on about 12 years was against a TRN. The inspector ended up telling the appellant to be quiet and accept the free advice she being given and she kept coming up with nonsense off the internet that was really easy to discredit. 

2005 said it may be acceptable to offset by up to 20% for open grown trees only. What everyone took from that was "blah blah acceptable blah blah 20% blah blah".

 

As I have already said, the offsetting of a circular RPA by 20% in distance only makes a difference  of 5% of the RPA. Mathematical formula available if anyone wants it. Mathematical prioof available if anyone really really wants it.

 

Just as big a problem as I see it is the failure to offset RPAs when all the evidence is there that the tree has done this naturally due to physical constraints. This can leave the true important rooting area in the path of development where no precautions are specifed to avoid loss and damage.

 

If and when 5837 is reviewed the focus should shift from allowing justified offsets to requiring them.

[Chris at eden]

2 minutes ago, daltontrees said:

2005 said it may be acceptable to offset by up to 20% for open grown trees only. What everyone took from that was "blah blah acceptable blah blah 20% blah blah".

Even worse, some took it as they can reduce the RPA.  But yes it was abused.  The key difference for me is that the 2005 offset was to benefit the layout, the 2012 is the ensure that the most likely root morphology is plotted so that trees are properly protected.      

2 minutes ago, daltontrees said:

 

As I have already said, the offsetting of a circular RPA by 20% in distance only makes a difference  of 5% of the RPA. Mathematical formula available if anyone wants it. Mathematical prioof available if anyone really really wants it.

My point was that the 20% is not relevant and hasn't been for a long time.  You cant just say i am offsetting it as it was in a previous standard and then call it a good rule of thumb.  That was my only point.     

2 minutes ago, daltontrees said:

 

Just as big a problem as I see it is the failure to offset RPAs when all the evidence is there that the tree has done this naturally due to physical constraints. This can leave the true important rooting area in the path of development where no precautions are specifed to avoid loss and damage.

This  i agree with.  I have seen RPAs plotted beyond 2m retaining walls and under high rise blocks of flats.  its ridiculous.  You raise it as a TO and they come back saying - well, 5837 is only recommendations, what do they think recommendations actually mean.  I always offset RPAs but some consultants write whatever the client wants them to.  I've seen one recently where a chartered arb has recommended protecting less than half of the RPA as well as plotting the RPA under a road and retaining wall.           

2 minutes ago, daltontrees said:

 

If and when 5837 is reviewed the focus should shift from allowing justified offsets to requiring them.

Definitely