UKTC Archive

RE: Drop kerbs + Lime

Subject: RE: Drop kerbs + Lime
From: Rupert Baker
Date: Dec 29 2018 18:04:06
Hi Mark, I and a friend and fellow bell-ringer did the same on a huge Zelkova 
carpinifolia at his property outside Ashburton, after the Jan 1990 storm; dug 
out the root-pit (because the plate bulldozes soil into the middle of it as 
it rotates) and put it back pollarded quite heavily (8-10" diameter cuts), 
remaining height about 16-18m.  It is still there and growing happily, with a 
load of root suckers growing away as young trees around it; its now 20+m..

-----Original Message-----
From: <> 
On Behalf Of Mark Hudson
Sent: 29 December 2018 17:31
To: UK Tree Care <>
Subject: RE: Drop kerbs + Lime

Reference Jims extract from M&C re Lime and the drop kerb; during the 1987 
"hurricane" I was woods and parks manager at Hatfield park (Herts) and we had 
3 mature, apparently healthy (but not overmature) common lime blow over on 
the avenues - rather than lose them without a fight, and as we already had a 
tree contractor on site with matador (+ 10t winch) we "heavy pollarded" them 
back to about 6-8m (from distant memory), slightly enlarged by excavator the 
crater left by the blown root plate, winched them back upright and refilled 
any remaining crater still open

They survived and continued to grow for at least 4 1/2 years, I moved on in
1992 so don't know what the longer term held for them - and yes, I am aware 
there will have been a multiple of entry points for pathogens thereafter

Again, from distant memory, upended root plate radius was c. 1.5 - 2m

Can't claim it as anything like replicated research, rather works carried out 
on a "worth a try" basis as we had lost so many trees that night

If it was today, I would have air spaded radial trenches out to maybe 10m 
every 2-3 years to assess root redevelopment, if they survived......


-----Original Message-----
[] On Behalf Of Jim Quaife
Sent: 28 December 2018 12:03
To: UK Tree Care
Subject: RE: RE: Drop kerbs

Vehicle crossovers on highway land have to be adoptable.  To that end one has 
no choice but to use the Highway Authority's specification.  I am involved 
with a bit of a tussle currently and it is interesting that the depth of 
excavation required is 230mm.  Whereas 5837 is concerned about areas, roots 
actually occupy volume.  Accordingly I reach my opinions having discovered 
the rooting depth profile.  If, as in my current case, the roots are still 
present at a metre deep, I stopped digging because that said to me that the 
loss of the roots in the top 230mm is unlikely to be significantly harmful.
Don't forget to think about the entire root system, and also that the species 
in your case is lime, which is recorded by Matheny and Clark as attached.
I am not saying that all crossovers are acceptable, but to repeat the closing 
sentence in a past article of mine: if all you need is a calculator, why do 
you need to know anything about trees?

-----Original Message-----
[] On Behalf Of Julian Morris
Sent: 28 December 2018 11:37
To: UK Tree Care
Subject: Re: RE: Drop kerbs


With caution, APN12 conflicts substantially with BS5837.

Drop kerbs and their foundations will remove roots. Are these roots and the 
rooting volume around them essential to maintain the vitality of the trees?
I believe BS5837 4.6.3 (a) and (d) could provide a solution (if one can be 
provided that doesn't involve a no-dig one).

Julian A. Morris - Professional Tree Services  and
0778 XXX XXXX - 0141 XXX XXXX

Sent: Friday, December 28, 2018 at 10:14 AM
From: "Jasper Fulford-Dobson" <>
To: "UK Tree Care" <>
Subject: RE: Drop kerbs


I've had the same issue to deal with before. 

Avenue of TPO limes on a narrow semi-rural residential road with large
detached houses, many of which had been rebuilt or in-filled over the 
previous years, with 2-3 dropped kerbs between the trees setting the 
precedent. LPA's tree officer pointed out that the other examples had been 
done before the 2012 revision of BS5837 so "precedent" could not be used as a 
viable justification, raised concerns about how the levels would match 
("no-dig" construction to ramp up over the RPA from the existing road level), 
suggested the trees would be adversely impacted and objected with no room for 
manoeuvre. The application was refused and the client wasn't prepared to test 
this at appeal.

Suffice to say (as others have experienced) all trees near the 
dropped kerbs are in fine and healthy condition, despite the level changes 
being very subtle.

Despite the expectations of some, as arb consultants all we can do is 
and help guide the process by setting out the principles to take to reduce 
the impact on trees. Make sure you re-read Tree Roots in the Built 
Environment, BS 5837, APN12, Built Environment ( and 
Geosynthetics info/case studies then consider the special engineering 
solutions available that might help overcome or mitigate your problem. Put 
these forward to your client's designers making it clear you are not an 
engineer or landscape architect and advise them to prepare additional cross 
sectional drawings (before and after) showing the built structure and the 
level changes, especially how they can be matched. 

Good luck.


-----Original Message-----
<> On Behalf Of Paul Hawksford
Sent: 24 December 2018 22:09
To: UK Tree Care <>
Subject: Drop kerbs

I've a site with a proposed residential dwelling, unfortunately, the
architect also proposes a couple of drop kerbs in the public footpath outside 
leading into the access driveway. The kerb would be sited within the RPA of 
two nice mature lime trees which sit in the footpath. Drop kerbs have been 
installed in the same area, some ten years ago and very close to similar 
trees along the road and he's hoping this will help the application.
I've dealt with drop kerbs before and viewed them with a cautious eye, 
consequently, I told those architects it would be difficult to convince 
planners that it could be done sympathetically. Has anyone experience, or 
produced a method statement for this...?


Paul Hawksford
Principal Arboriculturist

16 Ballydonaghy Road

County Antrim
BT29 4EP

M: +44 (0)7746 XXXXXX


P Please consider the environment - do you really need to print this

Please be GREEN and leave it on the SCREEN


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The UKTC is supported by Bosky Trees arboricultural consultancy