Transcript The long hot summer of 1976 that eventually ended in

GETTING TO GRIPS WITH
SUBSIDENCE
Dr Giles Biddle
and
Dr Martin Dobson
Introduction and background to
subsidence problems
Dr Martin Dobson
Our story begins in the 1970s…
…when fashion sense was questionable
and subsidence became an ‘insured peril’
It continues in 1976…
…which coincides with the first commercial
flight of Concorde on 21 January
…with the formation of
Apple Computers on 1 April
…with water rationing in Cardiff
on 9 August
1976
The long hot summer
of 1976 was the
longest recorded
in England and Wales
since 1727.
1976
For several weeks
in July and August,
large parts of the
country got no
rainfall at all
leading to the
drying up of
reservoirs and a
severe drought.
Staines reservoir
1976
Finally the Labour
government of the
time appointed a
minister for
drought…
Denis
Howell
…as if on cue the rain began to fall.
SUBSIDENCE
SUBSIDENCE
What kind of damage are we
talking about?
500
Number of claims (1000s)
450
Cost of claims (£million)
400
350
300
250
200
150
100
50
2002
2000
1998
1996
1994
1992
1990
1988
1986
1984
1982
1980
1978
1976
1974
1972
0
Legal framework
Case law (common law)
Trespass
Trespass
A trespass is the
wrongful invasion of
another's property.
Every unlawful entry
onto another's
property is trespass,
even if no harm is
done to the property
Trespassing
root
(naughty!)
Nuisance
Nuisance
Unfortunately trees can’t read!
Nuisance
A private nuisance is
an interference
with a person's
enjoyment and
use of his land.
Negligence
A person has acted negligently if he/she has
departed from the conduct expected of a
reasonably prudent person acting under
similar circumstances
Reasonable Foreseeability
a danger which a reasonable person should
anticipate as the result from his/her action or
inaction
Solloway v Hampshire County Council
(1981)
HCC were appealing against a previous judgement made against them
in favour of a home owner Mr B. Solloway.
Subsidence damage had been caused to the house by a Horse
Chestnut owned by HCC.
Judgement was made that the encroachment of the tree roots
constituted a nuisance and HCC were responsible for damage caused.
However, geological maps showed that whilst the house was on plateau
gravel sections of it rested on small pockets of clay which were not
shown on geological maps.
The Court of Appeal ruled that the existence of small clay pockets
beneath the house was not reasonably foreseeable and hence there
was no breach of duty on the part of HCC. The appeal was allowed.
Paterson v Humberside County Council
(1995)
Damage to a house caused by two Lime trees owned by Humberside
County Council.
It was noted that although the house had shallow foundations and was
thus more susceptible to damage this had no relevance to liability – ‘the
tree takes its victim as it find it’
An argument was made on behalf of the plaintiffs that there was no need
to establish foreseeability. This was rejected by the judge who said the
test for such foreseeability was whether the risk was one which a
reasonable person in the defendants position would have regarded as a
real risk.
The Council was deemed to know that damage was a ‘real risk’ as it
advised householders of safe distances from buildings to plant trees.
Delaware Mansions v Westminster City
Council (1999)
In 1989 a Plane tree owned by Westminster City Council caused
damage to some flats. Engineers recommended underpinning of the
flats or removal of the tree. The council refused to remove the tree.
The flats were sold in June 1990 to the second appellant company for
one pound. However, their claim for damages was dismissed on the
grounds that they could not claim because the damage had occurred
before they became the owners.
The plaintiffs appealed and won. "Thus, where there is a continuing
nuisance, the owner is entitled to … damages "
"If the council had agreed to remove the tree when asked, the damages
would have been very small…the fact that the nuisance existed before
the second appellant became the owner is irrelevant".
Jones v Portsmouth City Council (2002)
The key issues were whether subsidence had been caused by the
defendant’s Plane trees, whether the council were responsible and
whether or not the council had been given sufficient notice to abate the
nuisance.
The judge ruled that the trees had caused damage and that despite the
soil being ‘brick earth’ it was a foreseeably shrinkable soil.
On the matter of reasonable notice to abate the judge said:
‘the fact is that the defendant was notified of the claim before the
claimant was committed by contract to the underpinning ’ and therefore
‘the defendant was not deprived of a reasonable opportunity to abate the
nuisance’ .
Loftus Brigham v London Borough of
Ealing (2003)
The issue was subsidence caused by either the claimant’s Virginia
creeper and/or Wisteria or the defendant’s Plane trees
Original ruling - ‘The Claimants need to show that the Defendants’ trees
were probably the dominant cause and they have not convinced me that
such was established’
On Appeal the ruling was that the proper test was whether the tree roots
were the ‘effective and substantial’ cause of the damage or alternatively
whether they ‘materially contributed to the damage’.
Raphael v London Borough of Brent
(2007)
The issue was whether level monitoring only was adequate to establish
that subsidence had occurred.
There were no soil, foundation or root investigations. Neither was any
crack monitoring carried out.
The secondary issue was which vegetation caused the damage. Was it
the claimant’s Wisteria and Cherry or the council’s Plane(s)?
The judge ruled out the claimant’s vegetation as a cause of damage and
gave judgement against the council.
PLANE
CHERRY
London Tree Officer’s Association

Identify those trees that are most likely to
cause subsidence damage and subject
them to a regular and systematic pruning
regime.

Make the identification of the above trees an on going process
within the normal tree inspection programme.
Investigate all potential subsidence claims that may implicate
trees and take prompt action (i.e. investigate the site and, if
appropriate, carry out precautionary pruning). If ground
conditions recover subsequent to precautionary pruning the
potential claim may not be lodged. By taking prompt action
boroughs can eliminate or mitigate a potential claim.
All claims should be assessed and remedial pruning carried out
as soon as practically possible, except where the claims are
clearly unreasonable or erroneous.
Before undertaking further pruning or contemplating tree removal
the authority should insist that the claimant provide adequate
evidence in support of the claim.




Identify those trees that are most likely to cause subsidence
damage and subject them to a regular and systematic pruning
regime.

Make the identification of the above trees
an on going process within the normal
tree inspection programme.

Investigate all potential subsidence claims that may implicate
trees and take prompt action (i.e. investigate the site and, if
appropriate, carry out precautionary pruning). If ground
conditions recover subsequent to precautionary pruning the
potential claim may not be lodged. By taking prompt action
boroughs can eliminate or mitigate a potential claim.
All claims should be assessed and remedial pruning carried out
as soon as practically possible, except where the claims are
clearly unreasonable or erroneous.
Before undertaking further pruning or contemplating tree removal
the authority should insist that the claimant provide adequate
evidence in support of the claim.




Identify those trees that are most likely to cause subsidence
damage and subject them to a regular and systematic pruning
regime.
Make the identification of the above trees an on going process
within the normal tree inspection programme.

Investigate all potential subsidence claims
that may implicate trees and take prompt
action (i.e. investigate the site and, if
appropriate, carry out precautionary pruning).
If ground conditions recover subsequent to
precautionary pruning the potential claim may
not be lodged.

All claims should be assessed and remedial pruning carried out
as soon as practically possible, except where the claims are
clearly unreasonable or erroneous.
Before undertaking further pruning or contemplating tree removal
the authority should insist that the claimant provide adequate
evidence in support of the claim.




Identify those trees that are most likely to cause subsidence
damage and subject them to a regular and systematic pruning
regime.
Make the identification of the above trees an on going process
within the normal tree inspection programme.
Investigate all potential subsidence claims that may implicate
trees and take prompt action (i.e. investigate the site and, if
appropriate, carry out precautionary pruning). If ground
conditions recover subsequent to precautionary pruning the
potential claim may not be lodged.

All claims should be assessed and
remedial pruning carried out as soon as
practically possible, except where the
claims are clearly unreasonable or
erroneous.

Before undertaking further pruning or contemplating tree removal
the authority should insist that the claimant provide adequate
evidence in support of the claim.





Identify those trees that are most likely to cause subsidence
damage and subject them to a regular and systematic pruning
regime.
Make the identification of the above trees an on going process
within the normal tree inspection programme.
Investigate all potential subsidence claims that may implicate
trees and take prompt action (i.e. investigate the site and, if
appropriate, carry out precautionary pruning). If ground
conditions recover subsequent to precautionary pruning the
potential claim may not be lodged.
All claims should be assessed and remedial pruning carried out
as soon as practically possible, except where the claims are
clearly unreasonable or erroneous.
Before undertaking further pruning or
contemplating tree removal the authority
should insist that the claimant provide
adequate evidence in support of the
claim.
Joint Mitigation Protocol
May 2008
Aims to:
Speed up the process of claims handling, decision
making and mitigation implementation leading to
resolution
Recognise the value of trees in the built environment
Provide local authorities with all the investigative
evidence required at the beginning of the process.
Joint Mitigation Protocol
May 2008
7 days
notify tree owner of damage
14 days
after receipt of notification tree owner to supply
details of:
- Contact person
- Insurer
- CAVAT value of tree - low (less than £5,300)
medium (£5,300 to £17,500) high (greater than
£17,500).
60 days
submission of evidence in support of claim
13 weeks
from receipt of the evidence to undertake the
mitigation.
ABI DOMESTIC SUBSIDENCE TREE ROOT CLAIMS
AGREEMENT
THIRD PARTY LIABILITY
Every insurer subscribing to this Agreement agrees 
1 that where a claim arises in respect of subsidence
and where damage to the building and/or contents has
been caused wholly or partly by tree root encroachment
the insurer holding the buildings and/or contents
insurance for the damaged property undertakes to
investigate, handle and where appropriate meet the
claim on the basis of their policy cover;

2
not to pursue recovery against the insurers of the owned/tenanted/ occupied property responsible for the
liability of the tree root encroachment regardless of whether the damage has been caused wholly or partly as a
result of the tree root encroachment;
3
that in the event of there being a recurrence of damage or no reasonable preventative measures being
taken by the person/persons who have liability for the tree root encroachment this Agreement will have no effect in
regard to any subsequent claim.
4
that this Agreement will have no bearing or consideration in any uninsured loss claim which may be
pursued against the person/persons having a potential liability for the tree root encroachment".


ABI DOMESTIC SUBSIDENCE TREE ROOT CLAIMS
AGREEMENT
THIRD PARTY LIABILITY
Every insurer subscribing to this Agreement agrees 
1
that where a claim arises in respect of subsidence and where damage to the building and/or contents has
been caused wholly or partly by tree root encroachment the insurer holding the buildings and/or contents
insurance for the damaged property undertakes to investigate, handle and where appropriate meet the claim on
the basis of their policy cover;

2 not to pursue recovery against the insurers of the
owned/tenanted/ occupied property responsible for the
liability of the tree root encroachment regardless of
whether the damage has been caused wholly or partly
as a result of the tree root encroachment;

3
that in the event of there being a recurrence of damage or no reasonable preventative measures being
taken by the person/persons who have liability for the tree root encroachment this Agreement will have no effect in
regard to any subsequent claim.
4
that this Agreement will have no bearing or consideration in any uninsured loss claim which may be
pursued against the person/persons having a potential liability for the tree root encroachment".

ABI DOMESTIC SUBSIDENCE TREE ROOT CLAIMS
AGREEMENT
THIRD PARTY LIABILITY
Every insurer subscribing to this Agreement agrees 

1
that where a claim arises in respect of subsidence and where damage to the building and/or contents has
been caused wholly or partly by tree root encroachment the insurer holding the buildings and/or contents
insurance for the damaged property undertakes to investigate, handle and where appropriate meet the claim on
the basis of their policy cover;
2
not to pursue recovery against the insurers of the owned/tenanted/ occupied property responsible for the
liability of the tree root encroachment regardless of whether the damage has been caused wholly or partly as a
result of the tree root encroachment;

3 that in the event of there being a recurrence of
damage or no reasonable preventative measures being
taken by the person/persons who have liability for the
tree root encroachment this Agreement will have no
effect in regard to any subsequent claim.

4
that this Agreement will have no bearing or consideration in any uninsured loss claim which may be
pursued against the person/persons having a potential liability for the tree root encroachment".
ABI DOMESTIC SUBSIDENCE TREE ROOT CLAIMS
AGREEMENT
THIRD PARTY LIABILITY
Every insurer subscribing to this Agreement agrees 

1
that where a claim arises in respect of subsidence and where damage to the building and/or contents has been caused wholly or partly by
tree root encroachment the insurer holding the buildings and/or contents insurance for the damaged property undertakes to investigate, handle and
where appropriate meet the claim on the basis of their policy cover;
2
not to pursue recovery against the insurers of the owned/tenanted/ occupied property responsible for the liability of the tree root
encroachment regardless of whether the damage has been caused wholly or partly as a result of the tree root encroachment;

3
that in the event of there being a recurrence of damage or no reasonable preventative measures being taken by the person/persons who
have liability for the tree root encroachment this Agreement will have no effect in regard to any subsequent claim.

4 that this Agreement will have no bearing or
consideration in any uninsured loss claim which may be
pursued against the person/persons having a potential
liability for the tree root encroachment".
Provided that:
(i) Immediate notice shall be given to the other insurer
by the insurer to whom the claim is notified, together with
copies of all relevant reports (including covering letters)
from loss adjusters, engineers, surveyors and the like.
Subsidence risk assessment
SRA developed by the Arboricultural Association
in 1998 in response to requests by the mortgage
and insurance industry
Withdrawn in 2001 as it didn’t accurately predict
subsidence risk
Subsidence risk assessment
Subsidence risk assessment
Subsidence risk assessment
SRA developed by Royal and Sun Alliance
TreeRAT
Subsidence risk assessment
6th September 2006 –new subsidence risk model, Arborisk™,
for Greater London (woo hoo!)
Aerial photography and Infoterra’s lidar1 height data has been
used to establish the proximity of trees to properties, as well as
the height and canopy size – from which the current and future
size of the root zone can be determined.
With this tree root zone data and soil type data, also included,
the model can quickly produce accurate (?) subsidence risk
assessments for individual properties.