A Way Forward
(or a better Protocol)
P.G. Biddle
Determining which remedy:
• Persistent deficit (significant heave)
– Underpin with full anti-heave precautions
• Seasonal drying (predominantly)
– Vegetation control
•
•
•
Fell
Prune
Root control
–
Underpin
(if
tree
of
sufficient
value)
P.G. Biddle
Information required:
• Seasonal or Persistent deficit
• Which vegetation is involved.
• If vegetation control, proof of whether it has
been effective.
• Extent and duration of heave.
• Extent of movement for partial underpinning.
• Appropriate level of proof for situation.
• Speedy resolution for house owner.
P.G. Biddle
Efficacy of investigations.
Prelim
Assess
P.G. Biddle
Trial
Soil
holes Invest.
Root
Ident.
Crack
monit.
Level
Monit.
Preliminary assessment
Pattern of damage
Time of development of damage
Probable geology (BGS survey).
Proximity and type of vegetation
If conclusion probably vegetation ……
P.G. Biddle
Efficacy of investigations.
Prelim
Assess
Seasonal or
persistent def.
Which vegetation

involved.
Whether remedy
effective
Extent and
duration of heave
Extent of partial
underpinning.
Appropriate

level of proof
Speedy resolution
P.G.
Biddleowner 
for house
Trial
Soil
holes Invest.
Root
Ident.
Crack
monit.

Level
Monit.




 









 


Other factors to consider:
Ownership of the tree:
Own tree
Third party
TPO or Conservation Area
Value of the tree.
P.G. Biddle
Value of the tree.
LTOA use CAVAT
Relevant to remedial options, not to
extent of investigations
If the owner values the tree, it is
worthy of proper investigation
P.G. Biddle
Other factors to consider:
Ownership of the tree:
Own tree
Third party
TPO or Conservation Area
Value of the tree.
Number of trees / shrubs
P.G. Biddle
Essential
Desirable
Useful but not necessary
Waste of resources
Scope of
investigations
Value
Owner
of
ship tree(s)
Own
Tree /
shrub
Third
Party
tree
Number
of trees
Low
Single
Many
High
Single
Many
Low
Single
Many
High
Single
Many
TPO or
Cons. area
P.G. Biddle
Single
Many
Level Crack
Monit. Monit.
Trial
hole
Root
Ident.
Plast. Desic. Desic.
index autumn other
Preliminary assessment sufficient
Application of level monitoring
Only if needed
Earlier!!!!
P.G. Biddle
Application of level monitoring
• Install level monitoring at first visit
• Level distortion survey if possible
• 2nd set of readings (after 6 weeks) :
• Initial diagnosis of pattern.
• Initial diagnosis of which tree(s) involved.
• Put TP on notice. TPO application or CA notification.
• 3rd / 4th sets of readings (after 12 / 18 weeks)
• Confirm diagnosis. Update TP and Local Authority.
• Consider need and location for soil investigations.
• Decide on and implement action.
• Continue monitoring to confirm efficacy.
P.G. Biddle
Level monitoring with late notification
9
Confirm
diagnosis
8
Movement (mm)
7
Action
6
5
Claim
notification
4
3
2
Set
up
1
0
O
P.G. Biddle
N
D
J
F
M
A
Initial
diagnosis
M
J
J
A
Confirm
efficacy
s
O
A Draft Protocol.
In any situation where tree-related subsidence damage is
suspected, level monitoring will provide the most relevant
and cost effective method of investigation. If any tree
suspected of involvement is deemed to be of value by its
owner, level monitoring should be the primary method of
investigation. It should be commenced at the earliest
opportunity.
Level monitoring on its own should usually be sufficient to:
1.
Confirm that the pattern of movement is
consistent with the influence of trees or shrubs
on a clay soil.
2.
Demonstrate the extent and spatial distribution
of foundation movement and its relationship to
any damage.
3.
Identify which trees or shrubs are likely to be
involved.
4.
Determine whether there is a risk of long-term
heave consequent upon tree removal.
5
If potentially relevant, identify the extent for
partial underpinning.
6.
Demonstrate whether remedial measures have
been effective.
Other methods of investigation, such as trial pits, soil
investigations for plasticity or determination of desiccation, root
identification, distortion surveys or crack monitoring are of
secondary importance. They should only be necessary if there
is any uncertainty in the interpretation of the results of level
monitoring. The scope of any such investigations should be
decided in the light of the ongoing monitoring results and
designed to resolve that uncertainty.
The results of level monitoring should be reviewed as each set
of readings becomes available. Decisions on remedial action
should be taken once the data is sufficient to show a pattern of
movement consistent with the implicated tree(s) or shrubs, and
then continued to determine the efficacy of the remedial action.
The timing and duration of readings should be determined on
such basis, and not to a pre-determined or fixed pattern.
If applied correctly, in most situations level monitoring will avoid
the need for other investigations, and will provide the most
cost-effective, reliable and speedy resolution to the problem, to
the mutual benefit of the home owner, tree owner and insurers.
In any situation where tree-related
subsidence damage is suspected, level
monitoring will provide the most relevant
and cost effective method of
investigation. If any tree suspected of
involvement is deemed to be of value by
its owner, level monitoring should be the
primary method of investigation. It
should be commenced at the earliest
opportunity.
Level monitoring on its own should usually be sufficient to:
1.
2.
3.
4.
5
6.
Confirm that the pattern of movement is consistent
with the influence of trees or shrubs on a clay soil.
Demonstrate the extent and spatial distribution of
foundation movement and its relationship to any
damage.
Identify which trees or shrubs are likely to be
involved.
Determine whether there is a risk of long-term
heave
consequent upon tree removal.
If potentially relevant, identify the extent for partial
underpinning.
Demonstrate whether remedial measures have been
effective.
Other methods of investigation, such as trial
pits, soil investigations for plasticity or
determination of desiccation, root
identification, distortion surveys or crack
monitoring are of secondary importance.
They should only be necessary if there is any
uncertainty in the interpretation of the results
of level monitoring. The scope of any such
investigations should be decided in the light of
the ongoing monitoring results and designed
to resolve that uncertainty.
The results of level monitoring should be
reviewed as each set of readings becomes
available. Decisions on remedial action
should be taken once the data is sufficient to
show a pattern of movement consistent with
the implicated tree(s) or shrubs, and then
continued to determine the efficacy of the
remedial action. The timing and duration of
readings should be determined on such basis,
and not to a pre-determined or fixed pattern.
If applied correctly, in most situations level
monitoring will avoid the need for other
investigations, and will provide the most costeffective, reliable and speedy resolution to
the problem, to the mutual benefit of the
home owner, tree owner and insurers.
P.G. Biddle
Risk assessment
P.G. Biddle
Castellain Mansions
Castellain Mansions
Datum April 1995
Movement Sept 1995
P.G. Biddle
Risk assessment
•
With suitable data, one can
identify overall degree of risk
•
But not which individual tree
poses that risk.
•
So should we be trying??
P.G. Biddle